Bioengineering Note.doc

CIVIL ENGINEERING IV/I

BIOENGINEERING PREPARED BY: DKB

CHAPTER : 01 INTRODUCTION TO BIOENGINEERING 1.1 INTRODUCTION Nepal is prone to natural as well as human induced hazards. Each year, several hundreds of lives and properties worth of several millions of dollars is lost, and the soil ecosystem is also disturbed. Earthquake, landslide, debris flow, glacier lake outburst flood (GOLF), avalanche and cloud burst take toll of life, property and flooding in the Terai. When such hazards occur, bridges, roads and power intakes located in the mountainous regions are destroyed. At the same time landslides and debris flows not only take the fertile field and houses but also add to the sediment load in the river, which in turn washes away the paddy fields located along the bank of rivers in mountain areas. In the Terai area, many paddy fields are either eroded or submerged with floodwater. In this context, it is a big challenge for engineers and technicians to solve the problem of erosion and slope stability. As it is too costly to construct heavy civil engineering structures and use high technology for solving these problems the experience of past several years have shown that using living plants can solve such types of problem. The use of living plants either alone or in conjunction with small-scale civil engineering structures or non-living plant materials for the purpose of reducing the shallow seated instability and controlling erosion on slopes of any watershed can be named as Bioengineering. It is not a new technique for Nepal. The indigenous methods similar to bioengineering are in practice for centuries. 1.2 IDENTIFICATION OF PROBLEMS ON SLOPES  Materials roll down the slope  Water enters into slope or liquefy the slope material  Loose state of materials  Outward and downward movement of slope  Slip of overlying layer  Accumulation of water

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INTRODUCTION TO BIO-ENGINEERING The use of living plants either alone or in combination with small scale civil engineering structures or non living plant material for the purpose of reducing the shallow seated instability and controlling erosion on slope. OR The use of live, woody and herbaceous plants to repair slope failures and to increase slope stability. Living plant material may be used alone or in combination with structural components such as rock, wood, concrete, or geotextiles. ENGINEERING FUNCTION TO BE PERFORMED FOR BOIENGINEERING  Catch Function  Armour Function  Reinforce Function  Support Function  Anchor Function  Drain Function

SCOPE OF BIO -ENGINEERING Bioengineering can be applied in different fields: slope stabilization on embankments and cut slopes, erosion control, water course and shoreline protection, wind erosion control, noise reduction, traffic control, mining and reclamation, construction sites, waste disposal and public health, reservoirs and dams, buildings, highways, railways . JUSTIFICATION CRITERIA FOR THE USE OF BIOENGINEERING

The use and application of bioengineering can be summarized as: 1. Reducing instability and erosion-

by observation in the field.

2. Increasing the slope’s factor safety-

by measurement in the field.

3. Physical flexibility-

by observation in the field.

4. Versatility in application-

by observation of a range of applications in the field.

5. Only solving some problems-

this may be difficult to evaluate.

6. Cost-effectiveness-

by cost comparison.

7. Environmentally advantageous-

by observation & comparison of sites in the field.

8. Socially advantageous-

by discussion with road corridor inhabitants and Extension groups

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Advantages of bioengineering  Protects almost all slopes against erosion  Reduces the instance of shallow seated instability  Improves surface drainage and reduces slumping  Physical flexibility  Versatility in application  The only solution for some problems.  Cost effective  Environmentally advantageous  Socially advantageous

LIMITATIONS OF BIOENGINEERING There are mainly four specific limitations of Bioengineering, that is, the aspects that are not dealt in bioengineering. 1. Vegetation in relation to buildings: 

Damage due to water removal on shrinking clay soils.



Root penetration on foundations and drains.



Risk of toppling into buildings.

2. Vegetation in relation to water quantity: 

Choking of waterways with plant growth as result of eutrophication.



The use of reed beds for land treatment of effluents and nutrient harvesting.

3. Vegetation growth on structure: 

Accelerates weathering and corrosion or causes adverse effects on the performance of concrete and steel.

4. Needs of aftercare:  

Vegetation cannot perform its engineering function in its initial stage. It demands regular repair and maintenance.

CONCLUSION Bioengineering is the appropriate and indigenous technique as well as a sustainable technology for slope stabilization. In spite of its beneficial characteristics there are some limitations, which should be considered in its design.

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CHAPTER: 02 Site Investigation 2.1 Analysis of slope stability based on Minerals Types INTRODUTION Minerals are naturally occurring crystalline chemical compounds. Rocks are aggregations of minerals. The mineral constituents of a rock may have very different chemical compositions and properties. A fresh rock sample may contain the following mineral groups:    

dark minerals; light minerals (milky); white mica (platy, translucent); quartz (sugary, translucent but can be milky).

Feldspar Feldspar

Dark color minerals

Feldspar

Quartz

Mica Light colored

Fig 6.6, Rock Containing Dark and light Colored Minerals Rocks are affected by weathering. Weathering is defined as 'The physical and chemical alteration of rock by the action of heat, water, and air'. Note that high temperature and high water content increase the rate of weathering.

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The relative order of susceptibility to chemical alteration in the common mineral groups is as follows: Dark minerals

Least resistant to alteration

Light minerals White mica Quartz

Most resistant to alteration

Rock resistance to weathering The weakness of rock has direct relation with the minerals types. The rock resistance weathering as per the minerals types is shown in following diagram.

Weak

Rock containing dark colored minerals • •

Dark colored igneous rock (Basalt) Dark colored metamorphic rocks containing mainly dark colored mica (gneiss, schist, phyllite, and slate)

•

Dark colored sedimentary rocks (mudstone, shale, siltstone)

Rock containing light colored minerals (granite, gneiss, phyllite, marble)

Strong

Rock Containing Mica (gniess, schist, phyllite, sandstone)

Rock Containing Quartz (mainly quartzite and sandstone)

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Slope stability as per Rock and Mineral types The slope stability of rock can be interpreted as per the rock and mineral types found on slope. The slope stability and soil formation sequence can be defined in the following manner.

Weak gentle slope

Slope of Dark colored less compacted rocks

High Soil Formation

Slope of Light Colored Rocks

Very stable peak and cliff Slope of rock containing more mica

Less soil Formation

(gneiss, schist, phyllite, sandstone)

Slope of Quartz rich rock (mainly quartzite and sandstone)

2.2 ANALYSIS OF SLOPE STABILITY BASED ON FRACTURE

ORIENTATION AND

Rock and Rock Fracture Rocks of the earth crust are subject to a number of internal and external forces. These forces activate during and after the formation of rocks. This interaction of rocks and the activate forces is responsible for a variety of features and structures developed in the rocks. The size, shape and arrangement of layers in rocks are resulted from a range of forces that might have acted on those rocks during or after their formation. The layered, simple or complex bending, warping, fracturing and displacements along definite planes, surfaces or zones formed by the action of internal and external forces within the rock are usually termed as geological structures. The rocks exhibit normally specific characters, features, and deformation or disposition patterns due to which rock masses show some features or design called structures. The study of the arrangement and significance of these features is termed as structural geology. It is a part of geotechtonics and in other terms it deals with the structure, movements and the development of the upper envelopes of the earth. Fractures are one of the major features of rocks. Most of the fractures are approximately parallel to each other and constitute what is called a 'set‘. Most rocks contain several fracture sets. Rock strength is related to the number and weakness of fractures. The presence of fractures is the main cause of failure of rock slopes. Friction along the interfaces between the fractures blocks governs the shear strength of the rock. Shear strength is reduced when contact along the interfaces is lost. Strong rocks have fewer fractures or

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closed and cemented fractures. A highly weathered rock may fail through the rock body rather than along the joints. Notice the following features of the rock (Fig 6.11 and Fig 5.12): 

Bedding



Orientation of structures



Fracturing and jointing

The orientation of these planes controls the resistance of the rock block failure to gravitational forces.

Joint

Bed

Bed Bedding Plane

Figure : Rock fractures and bedding

Bed

Bed Joint

Bedding Plane Bed

Fig 6.12, Bedding and fracture

Rock Fracture Measurement Strike and dip The strike is the direction of the line of intersection between a horizontal plane and the geological plane (bedding plane, joints, foliation etc). The dip is the maximum angle of inclination of the geological plane with respect to the horizontal plane measured on the vertical

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plane. The direction of dip and strike of any inclined bed must lie at right angles to each other. The strike and dip is illustrated in Figures. The dip of bed has two components direction and magnitude. The direction of dip, also called dip direction, is always right angle to the strike. A dip direction must be stipulated because a bed can dip one of two directions perpendicular to strike. The amount of dip is the angle which varies from 0o to 90o according to bed. The direction of dip is the geographical direction along which a bed has maximum slope. In case of horizontal beds the dip is 0o and for a vertical bed the dip is 90o. The maximum slope with respect to the horizontal plane is also called true dip and the direction is also called true dip direction. Similarly, any directions other than that of the true dip, and are less than true dip is defined as apparent dip. The representation of strike and dip in any geological map by the help of different symbols are shown in below. The dip direction and dip amount of a linear structure are termed as trend and plunge of the structures.

Figure: Strike and dip

a.

F

B N

E

O P

A

G

M

H

b.

Legend

F N

G

B

Siltstone

O E

M

A H

P

Sandstone

Fig :, strike and dip in strata ofdifferent position

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     

AB is the strike MOP is the dip angle OM is the dip direction Line OP lies on geological plane surface Line OM lies on horizontal surface EFGH is the horizontal surface



During data measurement of strike and dip and are referred in text mainly by two notations. a. Strike notation i. N55oW/35oS : Strike north 55o west and dip 35o due south Figure: Strike and dip plot of the Fig 5.4 ii. 305o/35oS : Strike azimuth 305o and dip 35o due south. b. Dip notation i. 35o/S25oW : Dip 35o and dip direction 25o west of south ii. 35o/205o: Dip 35o and dip direction has an azimuth of 205o "ii." can also be referred as 205o/35o i.e. dip direction 205o and dip amount 35o and widely used in mathematical treatment of strike and dip. There are a number of ways to determine the attitude of a structural or geological plane, and all are based on field measurements of one kind to another. The most direct method is to hold the compass directly against an exposed plane surface at outcrop, for strike, one edge of the open compass is placed against plane and the compass rotated until it is horizontal. In general, for the measurement of strike, the compass should be parallel to the strike line and for measurement of dip angle or dip amount the compass should be vertical along the dip line . The trend given by its bearing or azimuth, this position gives the strike direction. Similarly, dip is determined by placing one side of the compass box and lid directly against the exposed plane perpendicular to the previously measured strike. The clinometer bubble is leveled and the dip angle read.

Inclined Geological e

Lin Strike

ip D

Plane

ne Li

pass Com gical Geolo

Figure : General view of Brunton Compass (Source: The Brunton Company, 1989)

Figure : Measurement techniques of Strike and dip

by Geological Compass

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Rock Joints (Fractures) Joints are surface along which no lateral movement has occurred and are found in practically all rocks. Commonly, they are found in joint sets, related by their orientation with respect to the stresses operating in an area. Because joints are relatively open, they are commonly filled with minerals. the infilling tends to reduce shearing resistance and along the joint surfaces. A groups of joints which runs parallel to each other are termed a joint set whilst two or more joint sets which intersect at a more or less constant angle are referred to as a joint system.

Joint Sets Systematic sets should be distinguished from non-systematic sets when recording the discontinuities in the field. Barton (1978) suggested that the number of sets of discontinuities at any particular location could be described in the following manner 1. Massive, occasional random joints 2. One discontinuity set 3. One discontinuity set plus random 4. Two discontinuity sets 5. Two discontinuity sets plus random 6. Three-discontinuity sets 7. Three discontinuity sets plus random 8. Four or more discontinuity sets 9. Crushed rock, earth-like.

Fig 6.18, Joint System in the surroundings of a Tunnel Fig 6.19, One set of Joint

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Fig 6.20, Joint in a Gneiss boulder and opening is 3 to 5 cm wide

Fig : Three set of joints

Fig :Three set of joints in rock exposure

Joints

Fig : Wedge failure in rock exposure

Fig : Joints in rock exposures

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Plane Failure

Wedge Failure

Toppling Failure

Fig : Various Types of slope failure due to Joints in rocks

Rock Behaviour: Surface The rock mass (jointed rock) has typical failure characteristics according to low and high stress conditions. Following figures are the examples of fractures and failure relationships.

Massive

Jointed

Heavily Jointed

Low Stress Condition Massive

High Stress Conditions

Jointed Heavily Jointed

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2.3 ANALYSIS OF SLOPE STABILITY BASED ON WEATHERING GRADE INTRODUCTION The mineral constituents of a rock may have very different chemical compositions and properties. A fresh rock sample may contain the following mineral groups: • • • •

dark minerals; light minerals (milky); white mica (platy, translucent); quartz (sugary, translucent but can be milky).

The rocks with such different minerals generally lead to weathering process and creates thick soil formation above the bed rocks. Weathering is defined as 'The physical and chemical alteration of rock by the action of heat, water, and air'. Weathering is an umbrella term for the processes which wear rock and other materials down and break them apart. It happens because rocks and minerals which formed at one set of conditions are not necessarily stable at other conditions; more correctly, the rocks and minerals are not in equilibrium with the environment around them. Weathering is the process by which rocks and minerals become equilibrated with their surroundings. High temperature and high water content increase the rate of weathering.

A weathered rock sample will show some or all of the following features:

    

softness ( i.e. minerals can be rubbed off by hand); discoloration; loosening of grains; intact white mica; intact quartz.

Types of Weathering There are generally three major kinds of weathering: Chemical Minerals making up a rock are chemically altered. They either transform to other minerals or dissolve.

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Physical/Mechanical Rocks are fragmented through generally inorganic mechanisms, while the chemical composition of the rocks' minerals does not change. Biological Living organisms can accelerate either of the previous two mechanisms.

Physical weathering

Product of Weathering Weathering of minerals creates more sophisticated minerals which play very active role in the slope stability. Such minerals are very active towards water and start to swell in even low low amount of water. Fig : gives list of weathering product of different minerals. Dark Colored Minerals

Clay Minerals and Iron Oxide

Light Colored Minerals (Feldspar)

Clay Minerals and K, Na, Ca, ions

Mica

Clay Minerals K ions

Quartz

Quartz

Calcite

CaCO3 ions

Fig. 6.8, List of weathering product

Weathering Phenomenon All denudation starts with weathering. Any loose material is immediately affected by gravity, so we can say that Weathering + Gravity => Mass wasting

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If a moving substance capable of transporting rock particles - a stream or consistent wind - is also present, then erosion takes place Weathering + Gravity + Moving fluid => Erosion Because of weathering, all rock surfaces (except for the very steep, and very young, geologically speaking) are covered by a layer of weathered material. Furthermore, presence of plants leads to formation of soil. As a result, natural surfaces are typically formed of several layers of materials

In Fig : From bottom to top we can see following pattern:

 Bedrock - solid unaltered rock.  Regolith - layer of weathered rock. o Residual regolith - weathered material derived directly from bedrock underneath (unmoved or moved very little). o Transported regolith (sediment) - weathered material moved and deposited by erosion (running water, waves and currents, wind, ice) as well as by mass wasting.  Soil - uppermost layer of regolith (1-3 m) enriched in organic matter From this figure we can say that weathering is a vital factor of slope development and it has direct link with slope stability.

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In Figure below we can predict soil formation process due to weathering on a slope

Fig: Slope development and soil formation

Rock weathering grades The weathering grade can be described in numbers and used as per following parameters

Weathering grade

Description

1a

Fresh rock. No visible sign of weathering.

1b

Faintly weathered. Discoloration on major joint surfaces.

2

Slightly weathered. Discoloration of all discontinuity surfaces or throughout rock.

3

Moderately weathered. Up to 50% of rock material decomposed and/or disintegrated to soil. Rock can be a continuous mass, or core stones.

4

Highly weathered. More than 50% of rock material decomposed or disintegrated to soil. Rock mass is discontinuous.

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5

Completely weathered. All rock material decomposed and/or disintegrated to soil. Original mass structure still largely intact.

6

Residual soil. All rock material converted to soil. Mass structure and material fabric destroyed.

`

Fig , Typical Weathering Profile

Conclusion Form this discussion, we can say More chemical weathering

More physical weathering

More soil formation

More rock fragment

More chance of slope failure related to soil

More chance of slope failure related to rock

formation

Rock type and slope failure A slope can be considered as rocky when even sparse outcrops of rock appear either directly at ground surface, within rivulets, or pointing out through a rather thin soil, which has originated from the underlying rock. For rocky slopes, stability greatly depends on the structure of the rock and on the geometrical relations between this structure and the slope. This is true at least for slopes with an incline greater than 38o - 45o degree, and is qualified by a variety of factors in equatorial and subtropical regions, where the weathering of rock is frequently deep and characterized by open fractures and laminations. In

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these regions, the transition from sound rock to proper soil is gradual and the entire cover is tied in with rock and its structure. For these reasons, equatorial and subtropical slope failures are chiefly ruled by rock mechanics in the mountainous areas. Except for simple cases, however (e.g. a layer of hard rock sliding on clayey rock), slope stability calculations are highly complex and often too theoretical for practical use. A new method for evaluating the risks of slope failure adapted to work in remote areas, was therefore tested during field work in Nepal. The method is laid out below. On slopes with inclines less than 38o - 45o degree water runoff is rather slow, and percolation through the rock increases and travel is deeper. Consequently, weathering becomes an important factor and thick layers of soil can be built up. Rock structure ceases to determine slope stability, and failures are then ruled by laws of soil mechanics. The same is true for slopes covered with thick allogenic material (debris, old landslides or rock-slides), morainic material and alluvium, although underlying rock structure sometimes continues to influence slope stability. When these soils are thin, however, stability may nevertheless be directly determined by rock structure. Under similar conditions, the surface areas of rock-slides and debris slides increase as the number of types of geological planes (laminations and fractures) and structural wedges increase. It can, therefore, be assumed that the risks of slope failure indirectly rise with the number of geological planes and structural wedges. Other characteristics are also~ important, however, and should be described in detail. In all, the main factors responsible for the failure of rocky slopes are: a)

Structural

b)

Lithological and mineralogical

c)

Hydrological

d)

Morphological

The Structural Factor Several rules can be stated concerning rock structure. The risk of slope failure rises as the number at types of geologic planes increases. The intersecting geological Planes from a structural wedge which is capable of leading to slope failure provided the inclination of the intersection is less than or equal to that of the slope. For slope failure to occur, the axis of intersection must parallel the direction of the slope, at least when only one critical wedge exists (see Fig below).

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BIOENGINEERING

40

40

o

o

50

Slope 240o/40o

Slope 130o/50o

30

o

o

Intersection between bed and fracture 135o/30o

Slope 200o/40o

Freedom of Movement of wedge 180o dip 40o in connection with cuts (road and river)

PREPARED BY: DKB

Intersection between bed and fracture 180o/40o

Freedom of Movement of wedge 180o dip 40o in connection with cuts (road and river)


No freedom of movement

60 40

o

o

No slide is theoretically possible when the incline of intersection is greater than the incline of the slope. A lateral or very lateral wedge is usually unable to create a slope failure.

The Lithological Factor Weathering, which is finally the root cause~-of landslides, depends chiefly on the lithological nature of the mother-rock. Logically, the types of rocks least subject to weathering are those constituted by hard minerals and by minerals non-reactive to acids. Quartzite is frequently the least weathered of rocks, precisely for this reason. On the other hand, mans, calc—schist and alternating layers of clay-origin rocks mixed with carbonate rocks are logically among those most prone to weathering, due to the dissolution of m calcite and clay minerals. Rocks of clay origin not only weather easily because of their lithological nature, but also because they are often fissile -i.e. they have a high number of cleavages. When bearing carbonaceous matter, these rocks weather even more readily. Gneiss and granite are subject to weathering under sub—tropical conditions because of the feldspars and ferromagnesium silicates they contain. When gneisses are interbedded with schist the potential of sliding is considerably increased. A statistical analysis, conducted along roads in the Mahabarat area, appears representative of rocks throughout the foothills of Nepal, and similar conditions may be found in other mountainous areas under tropical and subtropical conditions, from the results of the study a Lithological Coefficient for the Potential to Slide (LCPS) is obtained (Table). Table : Slide potential of Rock of Nepalese Mountains (source Krahenbunl J. and Wagner A., 1983)

Group

I

Rock type of Nepal

Slate, phyllite and schist, closely interbedded respected with calc-slate, calc schist, lime stone, dolomite and dolomitic quartzite.

Lithological slide potential

Very High (LCPS 16) High (LCPS 10)

II

Slates, phyllites and schists

III

Slates, phyllites and schists closely

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Medium (LCPS 5-10)



interbedded respect with quartzite and gneiss Medium to Low (LCPS 1 – 5)

IV

Gneiss

V

Quartzite

VI

Massive Lime stone and dolomite

Low (LCPS 1) Very Low (LCPS 0 – 1)

The lithological slide potential can be increased or decreased by the presence of minerals subject to weathering. By giving off sulphuric acid, pyrite (FeS2) is able to greatly increase the weathering even of quartzite, which can be considerably weakened in the process. Chlorite acts in much the same way, though less obviously, by oxidation. The presence of calcite in quartzite can be the determining factor for instability when inter-bedded with rocks of clay origin. In this case, the dissolution of calcite allows later to become more easily trapped by quartzite. Due to the presence of clayey layers, water pockets are then constituted, and these can create disastrous mass movements of rock. The presence of sericite, a kind of hydrous mica, can increase the potential to slide, as other micas seldom do. Graphite (carbon) can also increase the potential to slide, while carbonaceous matter (frequently containing pyrite) can, as stated above, increase the weathering of rock.

The Hydrological Factor The presence of water, whether as rivulets adjacent to, or as springs and seepages within weathered rock, obviously increases the potential of the occurrence of a slide. The quantifiable role played by the water factor is nevertheless difficult to analyze because rivu1ets, springs and seepages are~ often far from perennial, and thus may not be visible at the time surveys are carried out in tropical and subtropical climates. Nevertheless water plays a determining role at the time of occurrence of a slope failure. The shape of a slope is very important for assessing the Influence of water. Because they act as natural collectors, combs and concave slopes are in this sense more subject to slope failures than are crests and convex slopes. Rocks with open cracks and fractures, as well as those showing signs of karstic dissolution, easily collect water. Where these rocks are inter-bedded with layers of impermeable rock, especially in structural patterns prone to trapping water, major perennial or intermittent seepages or springs may appear. Large pockets of water may also accumulate within karsts. These conditions can rapidly deteriorate and lead to slope failure.

Fig Hydrological Factor for failure

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The Morphological Factor The incline of a slope is an important factor where the stability of rocky slopes is concerned. Experiences shown that about 80% of debris-slides and rockslides take place on hill slopes ranging from 30o to 65o, with a peak between 35o and 45o. Slides on originally rocky slopes with inclines less than 30o, at least subtropical areas are generally controlled by soil mechanics. Above 65o, rock-falls occur. As stated above in relation to water, the shape of a slope is also an important morphological factor for instability evaluation.

The forecasting of potential landslides according to Rock Fractures The factors with highest provability of leading to large debris or rock- slides (slumps excepted) car be summarized by the presence of  a structural slope  an incline of slope between 45o and 55o (other inclines should nevertheless not be excluded)  more than 3 - 4 geologic planes. The planes are open.  several structural wedges, arranged in a fan. At least one central or centro - lateral wedge is needed for a slide to occur. If the total of central and centro - lateral wedges is greater than the total of lateral and very lateral wedges, the slide will tend to be narrow and long. If the inverse is true, the slide will be broader.  rocks of clay origin closely interbedded with carbonate rocks and with or without detrital rocks (sandstones, quartzite end conglomerates)  rocks of clay origin or of clay and detrital origin closely inter-bedded  subsidiary minerals such as pyrite or graphite as well as chlorite and sericite  springs or seepages  a concave topography, as a more or less pronounced coomb. On the other hand, highly stable rocky slopes can be recognized by the combined presence of  a structural slope  not more than 2-3 geologic planes. The planes are “closed’, without fillings or coatings  no structural wedges, or exclusively lateral and very lateral wedges, or one centro-lateral or lateral wedge  unweathered or slightly weathered rock, including quartzite, massive limestone, dolomite and marble, as well as gneiss, phyllite and schist  an area free of water and unconnected with rivulets, springs or seepages  convex topography, humps, crests or ridges.

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There are of course a great variety of intermediate conditions existing between these two extremes. The above rules are immediately applicable for surveys of zones of limited extension such as bridge sites and any constructions of limited size.

2.6 INTRODUCTION TO MASS MOVEMENTS AND ITS CLASSIFICATION Slope Processes: mass movement and erosion Mass movement is a sudden, catastrophic, periodic removal of material toward down slope. It occurs due to failure in mass of slope. It can be surficial or deep-seated. It is often called ‘slope instability’, ‘mass wasting’. Erosion is a gradual, semi-continuous process. It is usually superficial, not deep-seated. It occurs because of loss of strength in the material. Erosion is generally called ‘hill slope processes’ or ‘soil erosion’.

Hill slope evolution Three end members have been proposed as general models for slope evolution: slope decline (Fig, A, B and C), slope replacement (Fig, E and F), and parallel retreat (Fig .D). It is possible to relate these end members with the diffusion. Slope decline is a solution to the diffusion equation with zero slope at the drainage divide and a fixed elevation at the base level. Parallel retreat is nothing more than the wave equation for weathering-limited slopes. Slope replacement is a mixture of the wave equation and talus accumulation. A

B

E

C

F

D

Fig: Hill slope evolution processes

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CLASSIFICATION OF MASS MOVEMENTS There are many classification schemes for mass movement (landslides) proposed by different authors like Campbell (1951), Hutchison (1968, 1969, 1977), Crozier (1973) and Varnes (1958, 1978). Hutchinson’s classification considers movement criteria including depth, direction and sequence of movement with respect to the initial failure. (Varnes 1978) Classification is based on nature of source material and the type of movement involved Types of Landslide/mass movement according to Varnes The types of landslide proposed by Varnes (1978) is the most commonly used in the world. It was also adopted by Landslide Committee, Highway Research Board, Washington, D.C. It divides landslides into falls, topples, slides, lateral spreads and flows. Wherever two or more types of movements are involved, the slides are termed as complex. Varnes (1978) has divided the material prone to landslides into classes, e.g. rock and soil. The soil is again divided into debris and earth.

Falls Falls are abrupt movements of the slope material that becomes detached from steep slopes or cliffs. Movement occurs by free-fall, bouncing, and rolling. Depending on the type of materials involved, the result is a rock fall, soil fall, debris fall, earth fall, boulder fall, and so on. Typical slope angle of occurrence of falls is from 45-90 degrees and all types of falls are promoted by undercutting, differential weathering, excavation, or stream erosion.

Topples A topple is a block or serial of block that tilts or rotates forward on a pivot or hinge point and then separates from the main mass, falling to the slope below, and subsequently bouncing or rolling down the slope. Table : Types of Landslide (Varnes, 1978) Type of movement

Type of material Engineering soils

Bedrock

Predominantly fine

Predominantly coarse

Falls

Earth fall

Debris fall

Rock fall

Topples

Earth topple

Debris topple

Rock topple

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CIVIL ENGINEERING IV/I Slide s


Rotational

Few Units

Earth slump

Debris slump

Rock slump

Translational

Few units

Earth block slide

Debris block slide

Rock block slide

Many units

Earth slide

Debris slide Rock slide

Lateral spreads

Earth spread

Debris spread

Rock spread

Flows

Earth flow

Debris flow

Rock flow

(Soil creep) Complex

(Deep creep)

Combination of two or more principal types of movement

Slides Although many types of slope movement are included in the general term “landslide”, the more restrictive use of the term refers to movements of soil or rock along a distinct surface of rupture, which separates the slide material from more stable underlying material. The two major types of landslides are rotational slides and translational slides.

Rotational slides These slides refer to a failure, which involves sliding movement on a circular or near circular surface of failure. They generally occur on slopes of homogeneous clay, deep weathered and fractured rocks and soil. The movement is more or less rotational about an axis that is parallel to the contour of the slope. Such slides are characterised by a scarp at the head, which may be nearly vertical. These slides may be single rotational, multiple rotational or successive rotational types, accordingly they may have a single surface of rupture, multiple surface of rupture. A “slump” is an example of a small rotational slide.

Translational slides These are non-rotational block slides involving mass movements on more or less planar surfaces. The translational slides are controlled by weak surface such as beddings, joints, foliations, faults and shear zones. The slides material involved may range from unconsolidated soils to extensive slabs of the rock and debris. Block slides are transitional slides in which the sliding mass consists of a single unit or a few closely related units of rock block that moves down slope. Translational slide may progress over great distance if conditions are right.

Lateral spreads Lateral spreads are a result of the nearly horizontal movement of unconsolidated materials and are

distinctive because they usually occur on very gentle slopes. The failure is caused by liquefaction, the process whereby saturated, loose, cohesionless sediments (usually sands and silts) are transformed from a solid into a liquefied state, or plastic flow of subjacent material. 24



Failure is usually triggered by rapid ground motion such as that experienced during an earthquake, or by slow chemical changes in the pore water and mineral constituents. Flows There are several types of flows and a short description of them is given below. a. Creep Creep is the imperceptibly slow, steady downward movement of slope-forming soil or rock. Creep is indicated by curved tree trunks, bent fences or retaining walls, tilted poles or fences, and small ripples or terracettes. b. Debris flow A debris flow is a form of rapid mass movement in which loose soils, rocks, and organic matter combine with entrained air and water to form a slurry that then flows downslope. Debris flow areas are usually associated with steep ravines where there are some active landslides. Individual debris flow areas can usually be identified by the presence of debris fans at the termini of the drainage basins. In general, the following conditions are important for formation of a debris flow: 

Slopes with 20-45 degrees



Saturated loose rock and soil materials with high content of clay minerals



High intensity and duration of rainfall

c. Debris avalanche A debris avalanche is a variety of very rapid to extremely rapid slide-debris flow process. d. Earth flow Earth flow has a characteristic “hourglass” shape. A bowl or depression forms at the head where the unstable material collects and flows out. The central area is narrow and usually becomes wider as it reaches the valley floor. Earth flows generally occur in fine-grained materials or claybearing rock on moderate slopes and with saturated conditions. However, dry flows of granular material are also possible e. Mudflow A mudflow is an earth flow that consists of material that is wet enough to flow rapidly and that contains at least 50 per cent sand-, silt- and clay-sized particles.

Complex movements A complex movement is a combination of two or more types of movements mentioned above. Generally huge-scale movements are complex, such as rock fall, rock/debris avalanches. The characteristic features of the types of landslides are simply illustrated in Fig.

25



2.7 INTRODUCTION TO LANDSLIDES Fig. 3.2, Types of Slope Movement (after Varnes 1978) 26



Landslide zones A landslide has distinct parts. Recognizing and assessing these individually helps us understand the character of the landslide, in particular, its severity. A landslide has four zones: -

zone of cracking (above the slide and sometimes around its sides)

-

zone of failure (the head scar (crown) and failure surface which may occupy only a relatively small area at the top of the slide)

-

zone of transport (a damaged slope, scarred by the passage of debris on its way down slope, this part of the slope may be stable, and may recover on its own)

-

debris pile (the detached, mobile material).

We describe the stability of a slope in terms of the factor of safety. Factor of safety 1 means that the slope is at the dividing line between being stable or unstable. If the factor of safety is more than 1 the slope is stable. If it falls below 1 it will be unstable.

Fig:, Parts of Landslides

Fig Landslide scenario 27



Fig: Fall Fig: Topple

Fig: Planar rock slide

Fig: Rotational slide

Fig: Soil Creep

Figure: Soil creep,28 tilted trees



Fig : Debris Flow, Matatirtha

Fig: Rotational slide

2.8 CAUSES AND MECHANISM OF SLOEPE FAILURE CAUSES OF FAILURE Landslides can be triggered by both natural and man-made changes in the environment conditions. The geologic history of an area, as well as activities associated with human occupation, directly determines, or contributes to the conditions that lead to slope failure. The causes of landslide can be inherent, such as weaknesses in the composition or structure of the rock or soil; variable, such as heavy rain, snowmelt, and changes in ground-water level; transient, such as seismic or volcanic activities; or due to new environmental conditions, such as those imposed by construction activities (Varnes and the IAEG, 1984). Among these factors, rainfall, earthquake and human activities are important trigger factors. Monsoon Rainstorm The Himalayas are affected by the monsoon, as are other parts of South Asia in general. Due to the recurring of the Summer Monsoon near the Bay of Bengal towards northwest, there is a general decrease in rainfall from East to West. Thus while Eastern Himalayas (Assam) have about eight months of rainy season (March-October), the Central Himalayas (Bhutan, Sikkim, Nepal and Kumaon) have only four months of rainy season (June-September) and in the Western

29



Himalayas (Kashmir), the Summer monsoon is active only for two months (July-August) (Chalise, 1994). Monsoon rainstorms initiate many landslide each year in the Himalaya region. During heavy rainstorm, loose/unconsolidated deposits, and strongly weathered and fractured sedimentary and metamorphic rocks become saturated and with an increase of precipitation and raise of ground water level. As a result, these materials are especially prone to sliding when slopes are steep. Rainstorms, therefore, are recognized as important landslide triggers in the Hindu KushHimalayan region. The relationship between rainfall and incidence of landslide has been studied by many scientists in China, India and Nepal. (Li and Li, 1985, Dhital et al, 1993, Joshi, 1997). The studies carried out in China show that If cumulative precipitation amounts to 50 mm to 100 mm in one day, and daily precipitation is more than 50 mm, somewhat small-scale and shallow debris-landslide will occur; When cumulative precipitation, within two days amounts to 150 to 200 mm, and daily precipitation is about 100 mm, the number of landslides has a tendency to increase with precipitation; and When cumulative precipitation exceeds 250 mm in two days, and has an average intensity of more than 8 mm per hour in one day, the number of large and vast landslides increases abruptly. Studying the relation between rainfall and landslides in China has also showed that under the same rainfall conditions, the landslides triggered have many differences in their quantity, size and density due to the different geological and topographical conditions. Therefore, the landslides have obvious regional characteristics. For a given region, the conditions of geology and topography are the decisive factors under which a landslide can be induced. The principal geological factors impacting on landslide process are the type of bedrock, crack and structure, soft band, the thickness of weathering zone, the thickness and the grain composition of the soil (the surface deposits). The impact of topographical conditions are represented in two respects. On the one hand, there are the regional cut depth, cut density and the erosion basis plane. On the other hand, there are impacts of the gradient and the form of slope and water convergent area on the upper part of the slope. Earthquakes The Himalaya mountain belt represents a type example of an orogen formed due to collision of two continents viz., the Asia and the India. The mountain lies in a major global seismic belt where earthquakes of magnitude 4.5 to 5.5 occur every year. In the region of Himalaya bounded by latitude 22N to 38N and longitude 72E to 98E, over 600 earthquakes of magnitude 5 and above have occurred during the period of 1950 to 1990. Till date four very major (great) earthquakes of magnitude more than 8 have been recorded in the Himalaya or adjacent regions.

30



These are the Great Assam earthquake of 1897, Kangra earthquake of 1905, Bihar-Nepal earthquake of 1933 and the Assam earthquake of 1950 (Thakur et. al. 1999). Earthquakes not only trigger landslides, but over time, the tectonic activity causing them, can create steep and potentially unstable slopes. It is recognized that significant numbers of landslides occur only when earthquake magnitudes are greater than 6. In the mountain areas, large-scale landslide triggered by earthquakes can block rivers and form lakes. Apart from the characteristics of earthquakes themselves (i.e., seismic accelerations, continuous time of shock, focal depths, and angle and direction of the approach of seismic waves etc.), environmental factors, such as geology, landform and drainage, play an important role in the formation of landslide induced by earthquakes. The influence of geology is reflected in both geologic structure and lithologic character. The landslides triggered by the Songpan earthquake (Aug. 16, 1976, M = 7.2), in northwestern Sichuan Province, can be taken as an example. The earthquake induced more than 170 slumps, slides, and falls, which occurred predominantly along the active tectonic faults in the strong seismic region (Fig. 1). On slopes consisting of loosened limestone and igneous rocks, the falls occurred readily, but on the slopes consisting of claystone, shale, and phyllite, the falls were few in number. Surface water Erosion, or soaking of surface to cause shallow sliding. Effects of water infiltrating from surface. Causes shallow failures. Various surface treatments, according to material type. Grass planting with or without the combination of jute netting and mulch for soils. Revetments for steep toe slopes in soil and soft rock. Surface renderings for rock slopes without noticeable ground water presence. Groundwater Ground water causes increased pore water pressure at depth. Failure plane is deeper than in surface water failure. Ideally, remove ground water by drainage. Weathering Rock shear strength is reduced by weathering. Rock strength is reduced as constituent minerals are broken down into weathering products and clay minerals. Physical bonds between rock constituents are weakened or broken. The rock can fail along weakened fracture planes or through its body. It is progressive process where cyclic failure possible and difficult to stabilize.

31



Undercutting Slope is undercut by a flowing stream or by the opening up of a road cutting. Incision (down cutting) or lateral scour by streams is a major cause of slope failure. The initial failure can work rapidly up slope. Stream bank and stream bed protection required. May be too late to save slope from progressive failure of up slope. Addition of weight Weight added usually by the dumping of spoil or landslide debris. Remove extra material and revegetate slope. FAILURE MECHANISM Erosion Removal of particles from the surface by flowing water is called erosion. An arbitrary depth limit of 25 mm has been adopted for erosion. This depth refers only to the initial removal of particles and is used to distinguish erosion from mass movements. If particles are continually washed away, the surface will be progressively lowered, giving rise to the forms of erosion described in 'a' to 'c'3 below. For example, a gully 2 m deep can be developed by the steady removal of particles from its sides to a depth of no more than 25 mm at a time. The process, which causes this, is still erosion. Sheet erosion Water flows over surface in an even film, not in channels. Vegetation stabilisation should be adequate. Rill erosion and gully erosion to less than 2 m depth Scour by water flow in channels. Gullies begin as very shallow, narrow incisions in the slope (rills). An arbitrary depth limit of 2 m has been set for gullies as erosion features. If a gully is deeper than 2 m, its sides fail in ways similar to a normal hill slope. Hill slope protection measures are then appropriate. Check dams to stabilise gully floor. Vegetation to stabilise gully head. Piping Removal of fines along an underground channel. Percolating ground water in permeable fine soils of low plasticity can remove fines along fissure to a point where an underground stream is formed. The roof of this stream cavern can enlarge upwards towards the surface and eventually collapse to create an open, elongated chasm or pit.

32



Difficult to stabilise unless underground waterways are exposed and treated as gullies. Even this will not stop piping in lateral channels. A deep interceptor drain can be considered.

:

Slide within soil or along soil/rock interface

Any mass movement of soil or debris down slope. Includes translational slides of soils or debris, rotational slumps, and flows. The plane of failure can be: -

within a soil or debris mass;

-

along the interface between soil and weathered rock;

-

the uppermost layer of weathered rock itself (in which case the failure plane would be in rock;

-

between soil and a rock plane in unweathered rock.

Translational slides are the most common form of slide in Nepal. In these a 'slab' of material of more or less uniform thickness slides off the surface. Translational slides are typically rectangular in plan, with a straight head scar and straight sides running parallel down slope. They are frequently quite shallow, i.e. one meter deep or less. They can be caused by ground water pore pressure along a slide plane or by weathering or undercutting of the slope. They can be shallow or deep, according to the structure of the superficial layers. A slump is a rotational movement of material, forming a spoon-shaped scar on the hillside, which is roughly circular in plan. The debris forms a bulge near the toe. Slumps are commonly caused by high ground water pore pressures deep in the hillside, and the slip circle usually goes several metres deep.

33



In practice in Nepal, deciding if there is a rotational or a translational mode of failure is usually extremely difficult. Many slides are a compound of the two types, in which a rotational component at the head degenerates into a translational component below. This is because coarse, non-plastic debris masses cannot sustain a circular slip plane except at the crown. Deciding which mode is dominant is useful because rotational failures indicate a deep failure plane and may therefore be more difficult to stabilise than a translational slide. Flows are caused by liquefaction of material, usually by the action of heavy rainfall upon a permeable soil surface. The soil literally flows down the slope. The failure plane is usually shallow, sometimes only a few centimetres deep. However, the fluid mass is very difficult to control or stop. Deep flows, which can travel a long way, are very destructive and potentially pose a high risk to life and property. For slides less than 100 mm deep, vegetation and/or bolsters should hold slope. Fences may become undercut by liquefaction.For slides 100 - 250 mm deep, diagonal vegetation may be sufficient to preserve rill system, provided maturity is reached. Support slope at base with gabion wall. Plane failure in rock Any mass movement whose failure plane or planes is controlled principally by fracture planes in rock, and whose debris consists chiefly of rock fragments. The weathering grade of the rock is 1 - 4 (the rock rings when struck with a hammer). Failure types commonly include plane failure, wedge failure, and toppling (rockfall). Standard rock mechanics procedure are the solutions. Disintegration A special type of rock failure, found in massive or sparsely-jointed permeable, weatherable rocks, e.g. porous sandstones, and in dense soils and unconsolidated materials that stand in a vertical or near-vertical face. Upon landing, the material breaks up into a pile of loose debris, consisting mostly of loose rock mineral particles e.g. sand containing a few boulders of weathering grade 4 or 5. All traces of rock structure or stratification are destroyed in the fall. For this reason the mechanism is distinguished from a fall of hard rock, which is considered a plane failure. Cause is weathering. Saturation and weathering cause the rock to fail by planar or arc-like shearing throughout the mass. Sometimes this is partially controlled by weakly developed joint planes. Strictly, the mechanism is a 'fall', but the form of failure is distinctive. The mechanism is typical of thick beds of soft Siwaliks sandstone and terrace deposits. It is very difficult to cure. It is very difficult to stabilize. Cut back to a stable angle, which is determined by shear strength of, saturated and weathered material.

34



Differential Weathering Weathering of rock layers whose susceptibility to weathering is strongly contrasting. This failure occurs typically in alternating thin beds of hard and soft rock e.g. sandstone and mudstone or siltstone. These formations are characteristic of the Middle Siwalik rocks of Nepal. The cause is a combination of weathering of the soft rock layers and plane failure of the hard rock layers. The soft rocks weather back from the face to leave the hard rocks sticking out. Eventually the hard rocks overhang so far that they break off along vertical fractures. The process then starts again and the whole face retreats. This mechanism is very common in Nepal.

Surface water

Toe Under cutting

Ground water

Weathering

Plane failure

Disintegration

Differential weathering

Piping and collapse

Fig 4.2, Causes and Mechanism of Failure

35

Addition of Weight



2.9 INTRODUCTION TO LANDSLIDE MAPPING This procedure will help you map an unstable site and observe all its significant features. The procedure is given in logical order but you do not have to follow this order in every case. An advantage of observing the site in a methodical way is that there will be less risk of missing an important feature. The column on the right suggests the action you should take.

The basis of the site record is a drawing of the site. A simple sketch will do. It does not have to be to scale. Its purpose is to help you to understand the geometric relationships between features of the landslide. It also enables you to record concisely your measurements and where you took them from. Any notes you make can also go on the drawing, but if they are lengthy, or if you wish to describe some detail of the slide by additional drawings and notes, these are best recorded separately in your notebook. It is good practice to make all your drawings and notes in one notebook. In this way pages do not get lost and records are kept in sequence.

Steps in a suggested procedure

Draw, measure or describe

Step 1

Draw

Geomorphic situation Look at the general locality and situation of the site: - make a note of the exact location so that you can direct others to the site if necessary; - see if it is in a part of the landscape where instability would be expected; - see if the orientation of the rocks, outcropping on the hillside around the site, indicate that the cause of the failure may be due to rock structure, either as planes of weakness or movement of water along fractures; - look at other sites in the area, they may have a similar geomorphic situation and a similar life progression.

36

Draw



Steps in a suggested procedure

Draw, measure or describe

Step 2

Draw

Sketch the site from the road or other good observation point:

- concentrate on getting the general proportions correct;

- estimate the length from top to bottom. Record this on the drawing; - estimate the width across the base. Record this. Step 3

Look for the landslide zones:

Draw

- scar; - transport; - debris.

Note that you cannot yet see whether there is a zone of cracking above the scar. You do not have to record these zones on the drawing, but the completed drawing should be sufficiently well illustrated and labelled to let another person recognise which zones are present and where they are. Step 4

Examine the material forming the original hill slope:

Describe,

- debris;

draw

- soft rock; - hard rock; - alternating hard and soft rocks. All of these could be present on one landslide. The drawing should show where they are.

37

Draw


BIOENGINEERING PREPARED BY: DKB Draw, measure or describe

Steps in a suggested procedure Step 5

Sketch a slope profile of the site from top to bottom. Angles do not have Draw to be real, but should indicate relative steepness. This can be augmented with more detail (e.g. with slope measurements) as you walk up the slide. Note that slopes >35° tend to be unstable unless of solid rock.

Step 6

Sketch the surface water drainage:

Draw

- streams; - any springs that may be visible from where you are standing. Step 7

Sketch areas of rock outcrop

Draw

Step 8

Landmarks:

Draw

- note any obvious landmarks on the site, such as prominent trees. This will help you to keep your bearings as you walk over and around the site. Step 9

Walkover survey Walk up the centre of the slide to the crown (head of Measure scar). Measure the angles of major slope units. If the slope is too steep or dangerous walk around the edge, looking into the scar.

38




Rock Visit each rock outcrop. Measure any relevant rock planes or observe how Measure the planes relate to the slope and failure planes.

Make sure that the rocks observed are true outcrops (attached to solid Describe rock beneath) and not simply large boulders partly buried on the slope. Note: - uniformity or layering (bedding) of the rock units; - degree of weathering (hardness) of the rocks; - degree of fracturing, especially any open fractures; - signs of water movement along fractures. Step 11

Debris and slope Indicate the area of the slide that is occupied by debris: - location and extent of landslide debris; - composition of debris; - wetness of debris; - depth of debris / depth of failure plane; - location, orientation and size of any cracks in the debris or on the slope; - any back-tilted slopes, where water may collect. (The presence of these indicates a ); - tilted trees. These can indicate tilted ground; - disrupted engineering structures, e.g. masonry surface drains; - points of ground water seepage.

39

Describe, draw




Margins and top Draw Look for: -cracks in the ground. Cracks are most frequent above the head of a slide, but they often occur also aro direction, the ground is under tension. The area of cracking tells you the area over which failure is about to take place; - streams, springs, irrigation canals or drainage structures, especially masonry drainage ditches. These features may be sending water into the slide. They may either have caused it in the first place, or they may be contributing to further failure. Irrigation canals and masonry drainage ditches should be inspected closely for any signs of cracking and leakage; - irregular topography, not due to rock outcrops. This may indicate the presence of an old landslide, in which case you will have to survey the whole of this, too. Continue up the slope above the landslide until there is no further evidence of instability. This may mean walking at least fifty metres higher than the landslide scar, and much further if necessary.

Step 13

Base of the slide Describe the features and ground conditions at the base.

Describe

Step 14

Causes and mechanisms of instability

Describe

Step 15

History and life progression of slide

Describe

Step 16

Severity of instability Fill in the scores on the Score Sheet for assessing severity of slope instability.

INTRODUCTION TO GULLY MAPPING The steps used for the landslide mapping can be equally used in gully mapping but more emphasis should be to size, water flow, gradient, gully materials, bank erosion, gully head location, and morphology of mouth.

40



In addition to above mentioned rules while mapping gully proper location of check dam construction is also necessary and following consideration must be taken into account: In a gully like below suitable site selection for check dam construction is a prime concern for mapping. The favourable site, which is generally called as Nick Point, should be identified during gully mapping. The debris deposit as well as probable modification of channel morphology area generally consider in identification of Nick Point. The details of point , B and C are given below.

A

B C

Location A is a 'nick point' in the gully floor, a point where the floor drops down suddenly after a relatively gentle gradient. A checkdam positioned here will hold up material for a long way upstream and further reduce the gradient. This particular nick point is composed of material which is softer than the sandstone bed. The slope below the checkdam would need to be very well protected with an apron to prevent scour of the nick point and undermining of the checkdam. The higher the checkdam, the greater is the need for scour prevention. Location B is a deposit of debris lying in the bed of the gully. Flowing water will move this downstream. A checkdam placed at the front of this debris pile will prevent it from moving further. This will have the effect of reducing the gradient of the gully floor and protecting it from scour. The danger then is that the stream will wander sideways and scour the bank, as discussed under the gully cross section, below. Location C is an outcrop of a harder bed of rock in the gully floor, producing another nick point. A checkdam can be built here for the same reason as at location A. However, an alternative would be to take advantage of the presence of a good foundation and simply armour the nick point against scour with a masonry lining on the gully floor.

41



CHAPTER: 03 BASIC ASPECT OF VEGETATION Aspect Aspect is the orientation of a site relative to the sun. In fact, this category relates to more than just aspect. It covers the environmental dryness of each individual site. The entire site moisture regime must be considered, although aspect is often the dominant factor in determining the site moisture. Other major factors are:      

Altitude; Rain shadow effect; Topographical location; Stoniness; Soil moisture holding capacity; and Winds and ex-monsoon rains.

Plant Community: A plant community is an established group of plant living more or less in balance with each other and their environment. The group can be natural or managed. The community is usually dominated by the main species of trees, but also contains lower plants such as shrubs, grasses and herbs. An ideal plant community for bio-engineering contains a carefully planned variety of different plants which together meet the engineering needs of site. The following things are to be considered for managing plant communities in bio-engineering:  Where possible, mixture of plants should be used in the initial planting. If relied on only one species this may fail, and there may by a complete loss of planted material.  It should be started with pioneer species. For example, with a damp and north facing slope utis and some under storey grasses should be introduced.  A balance of plant species in the community should be planned. Generally grasses, shrubs and trees should be included (but the exact balance is determined by the engineering requirements of the site).  Dominant plants such as utis must be replaced or thinned out within five to ten years. Otherwise the under storey plants will be overshadowed and eradicated completely, allowing erosion to start under the tree canopy.  The plants should be thinned out properly to maintain a balance.  Weeds should be cleared to reduce competition.  Gaps should be re-planted.

42



PLANT STRUCTURE:

BASIC REQUIREMENT OF PLANT : Water: Water is necessary for proper germination of seeds. Plants need water for growth.

43



Light :

Green plants need sunlight in to make their own food.

Nutrient:

Plants need the minerals found in soil for healthy growth.

Warmth:

Only grow well in the right conditions. Temperatures that are too cold or too hot may affect how the plant grows.

PLANT PROPAGATION: Plant propagation is the process of artificially or naturally propagating (distributing or spreading) plants . TYPES OF PLANT PROPAGATION: Sexual propagation—involves the exchange of genetic material between parents to produce a new generation. Asexual propagation—does not involve exchange of genetic material, so it almost always produces plants that are identical to a single parent. Sexual Propagation offers the following advantages:  It is usually the only method of producing new varieties or cultivars.  It is often the cheapest and easiest method to produce large numbers of plants.  It can be a way to avoid certain plant diseases.  It may be the only way to propagate some species. Collection and Methods:  Purchasing seed is the most common method used by gardeners.  Gardeners also collect seeds.  Seeds may also be harvested from healthy plants.  After harvesting seeds, they must be properly stored.  The germination of seeds is the next important step.  Some seeds require scarification in order to germinate.  Stratification involves exposing some seeds to lower temperatures and moisture.  Sowing seeds indoors is the easiest and cheapest way to grow certain plants.  Growing media is the material in which plants are grown.

44



 There are many types of containers used for starting seedlings.  The correct timing of sowing seeds is an important step in indoor seed starting.  There are many factors in the care of seedlings started indoors.  Seeds may also be sown directly into the garden.  Spores are a type of seed produced by certain plants like ferns.

Purchasing Seed:  It’s best to purchase seed for the current year.  Packages generally provide germination rates.  65% to 80% of seeds will germinate.  Of that number, 60% to 75% will produce seedlings.  Seed catalogs are very helpful in providing information on bloom time, germination requirements, cultural requirements and disease resistance. Bottom line, read packages carefully to purchase only the plants that meet your needs.

ASEXUAL PROPAGATION: Asexual propagation methods include cuttings, layering, division, grafting, budding and culture.  Leaf Cuttings and Leaf-bud Cuttings  Stem Cuttings  Root Cuttings  Division  Layering o Tip Layering o Air Layering  Grafting  Bulbs, Corms, Rhizomes, Tubers, Stolons

45

tissue



CHAPTER: 04 ROLE OF VEGETATION Introduction Any structure is constructed to fulfill a concrete function. This means, any structure has to fulfill its engineering as well as other functions. As described earlier in Bioengineering, small-scale civil engineering (inert) and vegetative structures are used. Generally, these structures are used for fulfillment of the following six engineering functions. Engineering function: It is the mechanical function performed by different parts of vegetation. Engineering functions performed by vegetation are as follows: a) Catch function Loose materials have the tendency of rolling down the slope because of gravity as well as erosion. Constructing any structure, which could catch the rolling down materials, can control this tendency. b) Armour function Some slopes are very water sensitive. It means, they start moving or are liquefied easily when they intercept water or there may be the case of high rate infiltration, which later causes shear failure. Therefore, such types of slope should be covered so that the water could be diverted easily. It is called the armoring function. c) Reinforcing function Because of presence of voids, the soil may not compact and it may need bonding of the grains. The structure constructed for this purpose fulfils the reinforcement function. d) Support function On the slope with length more than 15m, the lateral earth pressure causes the outward and downward movement of the slope material. Constructing any retaining types of structure can control this tendency. They fulfill the support function. e)Anchor function If there is a case of failure of overlaying layers with respect to stable underlying strata, the upper strata can be pinned up with the underlying ones. This activity fulfills the anchor function. f) Drain function Water is the main problem leading to instabilities on slopes. It could be the surface water or the ground water. Therefore, the water should be diverted safely from the slopes.

46



47



Engineering and Hydrological Function of Plant

Armour

Catch

Reinforce Support

Anchor

Figure: Engineering functions of plant

Cloud

Rain Interception Evaporation Store

Leaf drip Pool formation Infiltration

Water Uptake

Figure: Hydrological functions of plant

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1. Engineering Function: Bioengineering systems and civil engineering systems have similar functions. In other words, functions performed by civil engineering system can be achieved by bioengineering systems. The following task describes the various functions that could be achieved either by civil engineering structures or by bioengineering measures. Engineering function

Civil engineering system

Bioengineering system

Catch

Catch wall, catch fence

Shrubs, bamboo (any stems)

Armour

Revetment, surface rendering

Grass carpet (dense, fibrous roots)

Reinforce

Reinforced earth, soil nailing

Densely-rooting grasses and trees

Anchor

Rock anchors

Deeply-rooting trees (long, strong roots)

Support

Toe wall, prop wall

Shrubs, large trees (deep, dense root systems forming a soil cylinder)

Drain

Gabion drains

Plants are not currently used

Further more; there are two benefits of vegetation that are not obtained by civil engineering. These are:

 Environmental improvement: a cover of vegetation encourages other plants and animals to live on the slope  Limiting the lateral extent of instability: the rooting system of trees can interrupt the shear plane and stop it spreading further in the current phase of active instability. 2.Hydrological effects of vegetation: Plants are basic producers and provide food to the whole living world. In addition, they play important role in hydrological cycle and improves general environment of the surrounding. The effects in hydrological condition in and around a slope by plants are described in the following points.  Interception: rain strikes the leaves before striking the ground;  Evaporation: water may evaporate from the leaf surfaces;  Storage: water is held on the leaves and the stem for sometime before it eventually reaches the ground;  Leaf drip: accumulated water can drip off the leaves and fall to the ground;  Pool formation: water running over the ground surface may be trapped by stems and run-off prevented, pools will form on the surface;  Infiltration: the ground is roughened and loosened by stems and roots, enabling water to infiltrate more easily;  Water uptake: water is taken into the plant through the roots and returned to the atmosphere by the process of transpiration, which is the release of water through the leaves.

49



3. Mechanical Functions: a.

Roots bind soil and permeate the soil resulting in

-

Trapping of material moving down the slope;

-

Restraints of soil movement reducing erosion.

-

Effect: good.

b. Tall growth of trees so that weight may surcharge the slope, increasing normal and down slope force components. -

Effect: advantage in lower slope position but disadvantage for upper and middle slope positions.

c. Vegetation exposed to wind, dynamic forces are transmitted into the slope. -

Effect: good.

d. Stem and leaves cover the ground surface so that impact of traffic is absorbed. -

Effect: bad.

4.Hydrological Function: a. Foliage intercepts rainfall causing reduction in the kinetic energy of raindrops and thus erosive. -

Effect: good.

b. Roots permeate the soil leading to opening up of surface and increased infiltration. Effect: depends on site condition.

Role of vegetation: Modification of surface water regime  Interception  Surface water runoff  Infiltration  Subsurface drainage

Surface protection  Rain drop impacts  Surface water erosion

50



 Mechanical role  Soil insulation  Soil restraint Modification of soil water properties  Evapotranspiration  Soil moisture balance  Soil moisture depletion  Soil weight reduction Modification of soil mechanical properties  Root reinforcement of soil  Anchorage, arching, buttressing Modification of air flow  Change in the direction  Change in the velocity  Change in the contents  Change in the impacts

51



Soil strength and stability analysis :

52



ΔS= tR[sinθ+cosθ tanΦ] ΔS-the shear strength increase Φ-the angle of internal friction of the soil θ- the angle of shear distortion in the shear zone tR- mobilized tensile stress of root fibers per unit area of soil θ= tan-1(x/z)

tR =TR (AR/A),

AR  A

 ni ai A

TR   Ti ni ai  ni ai

 ΔS= TR (AR/A) [sinθ+cosθ tanΦ]  ΔS= 1.2TR (AR/A)  Lmin = TRD/4τb  τb = z*γ(1-sinΦ)ƒ tanΦ D- root diameter, TR –the root tensile strength, τb –the limiting bond ƒ- coefficient of friction between the root fiber and soil

53



Root strength:

Tr  nD m  Tr-root tensile strength o D- root diameter o n and m – empirical constants for a given tree species o n = 29.1-87,

m=(-0.76)-(-0.45)

 Strength loss with time following cutting  Trt = Tro e-bt o Tro -Tensile strength of root wood sampled from live trees o Trt -Tensile strength of roots sampled from stumps cut t months before sampling o b- probability of decay o t- age of stump (time between felling and sampling) o e-b –expression of the strength decay rate  t0.5 =log 0.5/log e-b o t0.5-the root strength ‘half life’ after felling

54



Quantification of soil arching:

Pr  0.5K oH z ( D  B)  pB * H z 2

p

H z cos  (m sin   m cos  tan 1  K o tan  )  (c1m  2c cos  ) 2ko cos  tan 

 clear B-spacing between trees  Hz-vertical thickness of yielding soil stratum  Ko-coefficient of lateral earth pressure at rest  γ - unit weight of soil  p- average lateral earth pressure in openings between piles trees on a slope  d- diameter of the embeded section of the tree  m =B/Hz, n=x/B  X-row to row distance between trees

55



Maximum allowable critical distance between tree piles

H z K o ( K o  1) tan  '  Bcrit  cos  (tan   tan 1 )  '

2c '



c '1 H z cos 

56



Root strength

57



EFFECT OF LOGGING

58



EFFECT OF CANOPY:

59



60



Hydrologicaleffect:

61



HYDRAULIC ROLE: Manning’s equation V=R2/3*S1/2/n  V-velocity of the flow  R-hydraulic radius  S- slope of the energy line  n-Manning’s roughness coefficient  Alternate friction factor  Darcy-Weisbach  Chezy

f=8*g*n2/R1/3

C=R 0.167/n and C= (8*g/f)1/2

Surface type

n

 Bare smooth soil

0.01

 5-10 t/ha of straw mulch

0.07

 Grass

0.2-0.4

o Depth of flow

n

o Shallow

0.25-0.3

o Up to oscillation

0.4

o Begins to submerge

0.01

62



Universal soil loss equation:  A=R*K*LS*C*P A-computed soil loss R-rainfall factor K- soil erodibility value L- slope length factor S- steepness factor C-vegetation factor P- erosion control practice factor Tensile strength of pinus radiata roots at different elapsed timee after felling: Root class

Mean tensile strength, Mpa

Mean root diameter, mm

Living trees

17.6

5.3

Cut 3 months

14.4

5.6

Cut 9 months

12.3

6.2

Cut 14 months

11.0

6.8

Cut 29 months

3.3

8.3

63



MECHANICAL EFFECT:  Soil reinforcement:  For Loretta grass ( lolium perenne)  C=10.54+8.63 log RD ---for sandy clay loam soil  C =11.14+9.9 log RD ---for clay soil  Role of organic matter  Root wedging  Arching and buttressing  Surcharging WIND LOADING:  D= ∑ (0.5*ρa*u2*CD *cos2 β *b) * l  D –drag force  ρa- density of the air  CD-the bulk drag coefficient of the vegetation  b-transverse width of the crown  u- wind velocity ,m/sec

64



STABILITY ANALYSIS

 Factor of safety without vegetation F

{C` (z -  w h w ) cos 2  tan `} z sin  cos 

 Factor of safety with vegetation F

(C`C`R )  {[ (z -  w h w )  W] cos 2   T Sin  } tan `Tcos {(z  w) sin  D} cos 

 C`R-enhanced effective cohesion due to reinforcement by roots  W- surcharge due to weight of vegetation  T-tensile root force acting at the base of the slip plane  D-wind loading force parallel to the slope  θ- angle between roots  hw- vertical height of GWT above the slip plane

65



CHAPTER : 05 PLANT SPECIES SELECTION Factors governing distribution of vegetation in nepal Plant type selection is a skilled job in bioengineering. There are more than 10000 plants in Nepal. About 6000 plants are easily available in all part of country. But there are only few and selected plants recommended for bioengineering. In Nepal, the vegetation bands are broadly related to altitude. The main factors, which govern the distribution of vegetation, are:  Altitude  Aspect  Rainfall and its distribution Geology and soils (relatively minor scale Distributions of plants in Nepal: Despite of very small country with an average width of 120 km from north to south .Nepal is very rich in biodiversity .The basic factors that lead to the special distribution of plant are as follow as. A) Ecological zone B) Altitudinal variation Depending upon the altitudinal variations different six vegetation zones are separated 1) Tropical zone 2) Subtropical zone 3) Lower temperate zone 4) Upper temperate zone 5) Sub alpine zone 6) Alpine zone c) Availability of moisture - Moisture loving plant like dhode - Draught resisting like babiyo, khar d) Consideration of land mass meeting e) Maintenance of plant community f) Prefer local species g) Availability h) Persistence

66



i) Growth characteristics j) Community participation k) Draught factor Vegetative zone:Although the classification of vegetation types is based on primarily on altitude but we don’t think that the altitudinal zones describe are rigid. Where two vegetation zones are meeting there is transitional zone where species from both zones occurs. Tropical zone:- It lies in upper boundary about 1000m.There is available Sal forest, other riparian forest, grass land and asana land. Subtropical zone:- It lies in the range of 1000-2000m in west and 1000-1700min the east. There is available khotesalla, chilaune, katus, utis riparian forest. Lower temperate zone:- The range of this zone is 2000-2700m in west and 1700-2400m in the east .Kashrus, gobre salla, lower temperate mixed broadleaf forest and banjh is the main plant which is available in this area. Upper temperate zone:- The range of this area is 2700-3000m in the west and 2400-2800m in the east. The main plants which are available in this zone are banjh, gurans, upper temperate coniferous forest and upper temperate broadleaf forest. Sub alpine zone:- 3000-4200m in west and above 3000m in east is range of this zone. Basically forest species are found growing in the cool desert area having a rainfall of less than 300mm/year.Small spiny shrubs are found in Mustang, Dolpa areas species include gurans, gobre salla and dhupi. Alpine zone:-This zone lies in above snow line. This area includes the species of gurans, dhupi, thorny plant and shrubby species. LOCAL SPECIES We can only produce a list of the locally available species in an area by carefully examining it. These are some of the local species that are found within the Kurintar area: Trees:

Sal, bhalyo, banjh, kavro, simali.

Shrubs:

Paineti, asuro, dhanyero, areri, dhusun

Grasses:

Sito, muse kharuki, kans.

67



Some grass species found on roadside slopes in Nepal

Altitude(m) Wet

Dry

2500

2000

1500

1000

500

0 Phurke Sito Amliso Setaria Muse kharuki Napier Khar Dhonde Kans Babiyo

68



Selection of Plant Species for Bioengineering Site

Site

Site environmental

requirements

conditions

Engineering functions

Availability of material

required

including ease of propagation Choice of

Human

vegetative techniques

General plant types which suitable

factors

Structural characteristics required

Range of possible species

69

Final choice ofspecies



SELECTION OF SPECIES BASED ON DROUGHT FACTOR Depending upon the drought factor, an appropriate species can be selected from the list provided in the Bioengineering Road Site Handbook, page 130-143.

70

CIVIL ENGINEERING IV/I a

b

c

d

Slope angle:

Stoniness:

Altitude:

Aspect:

BIOENGINEERING PREPARED BY: DKB Slope

Score

< 30º

1

30 - 34º

2

35 - 39º

3

40 - 44º

4

45 - 49º

5

> 49º

6

Fines

Score

> 25%

1

20 - 25%

2

15 - 19%

3

10 - 14%

4

5 - 9%

5

< 5%

6

Altitude

Score

> 2500 m

1

2000 - 2500 m

2

1500 - 1950m

3

1000 - 1450 m

4

500 - 950 m

5

< 500 m

6

Aspect

Score

North

0

Northeast

2

71


e


Annual rainfall:

Northwest

4

East

6

West

8

Southeast

10

Southwest

10

South

12

Rainfall > 2500 mm

1

2000 - 2490 mm

2

1500 - 1990 mm

3

1000 - 1490 mm

4

500 - 990 mm

6

< 500 mm

8

Highway slope site drought factor Classes: Score <6

Class I

Definition Cool, moist sites

6 - 11

II

12 - 17

III

Moderately dry sites

18 - 23

IV

Warm, dry sites

24 - 30

V

> 30

VI

Score

Damp sites

Very hot and dry sites Very severely hot and dry sites

72



CHAPTER :06 VEGETATIVE STABILIZATION TECHNIQUES INTRODUCTION The structures constructed for the purpose of slope stabilization and protection work with the use of living plants or plant materials are named as vegetative engineering systems. There are mainly three systems:  Bioengineering systems developed from the use of seed  Bioengineering systems developed from the use of seedlings  Bioengineering systems developed from the use of live cuttings VEGETATIVE SYSTEMS The systems used in bioengineering are as follows: Grass seeding or broadcasting, Horizontal lines of grass planting; Diagonal lines of grass planting; Down ward lines of grass planting Chevron lines of grass planting Herring bone lines of grass planting Random pattern of grass planting Shrub planting Tree planting Palisades; Brush layering

Horizontal Grass Planting on bunds

Fascines, Live check dam; Vegetated riprap; Live staking Bamboo planting Horizontal Grass Planting

73

Horizontal Grass Planting on risers



Diagonal Lines of Grass Planting

Mulch

Tree/Shrub Planting

Bruss Brush Layering Layering Palisade

74

Pit



IMPLEMENTATION OF VEGETATIVE SYSTEMS DIRECT SEEDING (GRASS AND SHRUBS) Grass Seeding The process is described in following points: 1) Prepare the site well in advance of the date of sowing. Remove all irregularities likely to allow slumps or gullies and clean loose debris away. 2) Immediately before sowing, scarify the surface of the slope. This means scratching the surface or carrying out basic cultivation to give a loose surface into which the germinating grass seeds can send their roots. 3) Spread the seeds or grass seed heads liberally over the slope. Ideally, the whole surface should be very lightly covered in seed material. An application rate of 25 gms per square meter is normal. 4) Cover the seeds completely with a layer of mulch, made from cut herbs such as Eupatorium adenophorum (banmara), or with hessian sheeting. Vegetation mulch is preferable. Shrub and tree seeding The process includes: 1) Clear all loose debris from the site, in advance of showing program. 2) Make a small hole, a little bigger than the seed, using a planting bar. 3) Push the seed right into the hole and cover it with soil; or, if it is in a rocky crevice, check that it is right out of direct sunlight. Make sure that the seed coat is not damaged in this process, 4) Seeds are normally shown at a rate of one every 25cm, center to center. PLANTING GRASS LINES The Process Involves the Following 1) Prepare the site well in advance of planting. Remove all debris and either remove or fill in surface irregularities so that there is nowhere for erosion to start. If the site is on backfill material, it should be thoroughly compacted, preferably when wet. 2) Always start grass planting at the top of the slope and work downwards. 3) Mark out the lines with string using a tape measure. Make sure they run exactly as required by the specification, whether it is contour, diagonal or downslope. 4) Split the grass plants out to give the maximum planting material. Trim off long roots and cut the shoots off about 10cm above ground level. Wrap the plants in damp hessian to keep them moist until they are planted. 5) With a planting bar, make hole just big enough for the roots. Place the grass into the hole, taking care not to tangle the roots or have them curved back to the surface. Fill the soil around them, firming it gently with your fingers.

75



6) If compost or manure is available, scatter a few handfuls around the grasses. If the site is very stony, this is important for improving early growth. You may have to incorporate it into the surface material to prevent it being washed off. 7) It looks rather dry and there is no prospect of rain for a day or two, consider watering the plants by a Jar

PLANTING SHRUB AND TREE SEEDLINGS RAISED IN POLYPOTS The process is described in following points: 1) Prepare the site well in advance of planting. Remove all debris and remove or fill surface irregularities. If the site is on backfill material, thoroughly compact it, preferably when it is wet. Cut all weeds. 2) If possible, dig pits for the shrubs or trees well in advance of the planting program, but refill them the same day. 3) When the ground is wet enough to support reasonable growth, plant out these seedlings. The bigger the hole made, the better it is for plant; but there must be a compromise between helping the plant and avoiding excessive disturbance to the slope. 4) Carefully remove the polypot by slicing it down the side with a razor blade to tear it carefully alone the join. Take care not to cut the roots. 5) Plant the seedling in the pit, filling the soil carefully around the cylinder of roots and soil from the polypot. Ensure there are no cavities. Firm the soil all around the seedling with gentle foot pressure. 6) If available, mix a few handfuls of well- rotted compost with the soil around the roots when you are back filling the hole. 7) Remove any weeds around the plant; add mulch so that it does not touch the stem.

PLANTING LINES OF HARDWOOD CUTTINGS (PALISADES OR “LIVE STAKING”) The process involves 1) Well in advance of the plating operation, trim and clean the site removing irregularities and loose debris. 2) With string mark out the lines to be planted. 3) Always start at the top of the slope and work downwards. 4) Using a pointed bar, make a hole in the slope that is bigger than the cutting and deep enough to take at least two thirds of its length. 5) Carefully place the cutting in the hole; preferably so that at least two thirds is buried firm the soil around it, taking care not to damage the bark. Ideally, only one node of the cutting or about the top 3cm should protrude from the soil. On steep, unstable sites, however, a greater protrusion helps to raise the delicate new shoots above the zone of moving debris and to trap more debris.

BRUSH LAYERING The process includes the following steps: 1) Using string mark the lines to be planted, starting 50cm from the base of the slope. 2) Always brush layer from the bottom of the slope, and works upward. 3) Form a small terrace, with a 20% fall back into the slope. The terrace should be 40cm wide. If you are brush layering a gravel-filled road embankment slope you should by a 5cm thick layer of soil along this terrace to improve rooting conditions.

76



4) Lay the first layer of cuttings along the terrace, with 5cm interval between the cuttings. Leave at least one bud and up to 1/3 of the cuttings sticking beyond the terrace edge and the rest inside. The branch growing tips should point towards the outside of the terrace. 5) Lay a 2cm thick layer of soil in between the cuttings to provide loose cushion. 6) Lay a second layer of cuttings on the top of this, staggered with the first layer. On a gravel-filled embankment slope, lay an 8cm layer of soil over the cuttings before you do any backfilling. 7) Partly backfill the terrace with the excavated materials. This should not more than 5cm thick. 8) Mark a line 1metre above the first brush layer and set the string for the next layer. 9) Follow steps 3 to 7. As the next terrace is cut, always fill the lower bench with the material excavated from above and compact it reasonably well by gentle foot pressure.

FASCINES The process involves the following points: 1) Well in advance of planting, prepare the site. Clear all loose material and protrusions and firmly infill depression. 2) Mark on the slope the lines were fascines are to be installed. Supervise workers carefully to ensure that the lines follow the contour or desired angle precisely. 3) Always construct fascines from the bottom of the slope and work upwards. 4) Dig about 5 meters of trench at a time, carrying out Step 5 at the same time. This ensures that the soil in the trench is exposed only for a short period, retaining residual soil moisture. The trench should be about 20cm deep and 20cm wide. 5) Lay the cuttings together, filling the trench and with their ends overlapping so that they form a single cable right across the slope. Four cuttings per bundle are normal, but sue eight per bundle if there is a lot of material available or if the site is very critical. 6) The fascines can be bound as first laying strings across the trench and then tying it when the cuttings are in place install them. This helps to keep the cuttings together during backfilling but is not essential. 7) Backfill the trench as soon as possible, lightly covering the cuttings, and tamp the soil down firmly around it. 8) If the slope angle is more than 250, you should peg the fascine. Hammering a large cutting into the slope immediately below the fascine can do this. Use one peg per 50cm run fascines.

PLANTING BAMBOO CULMS CUTTINGS The process involves the following points: 1) Keep the root ball wrapped in wet hessian until you are ready to plant it, so that it does not dry out. 2) Remove all the loose debris from the site and carry out any other site preparation well in advance of the planting day. 3) Dig a sufficiently large hole and plant the cutting in it. 4) Carefully backfill the hole, making sure that buds are not damaged to the base of the cutting. Firm the soil. 5) Place a layer of mulch over the disturbed soil and the surrounding area. 6) Water thoroughly. 7) Do not place bamboo cuttings closer than 2m apart across the slope or 5m up and down it.

77



LIVE CHECK DAMS The process involves the following steps: 1) Choose the location for the live check dam so that the maximum effect can be achieved. 2) Make a hole deep and big enough to insert vertical hardwood cuttings of the largest size available (truncheon cuttings of up to 2 meters in length are best). Use a crowbar if necessary to extend the hole. 3) Insert the vertical cuttings by carefully pushing them into the hole and firming the soil around them. Try not to damage the bark. They should protrude about 30cm above the ground surface. 4) Place fascines or long hardwood cuttings on the uphill side of the vertical stakes. 5) Key these horizontal members into the wall of the gully. 6) Backfill around the check dam and compact the soils with foot pressure.

78



DESIGN ASPECTS OF VEGETATIVE ENGINEERING STRUCTURES System

Functions

Method of operation

Applications and site requirements

Time to maturity

Limitations

Horizontal line grass planting

Catches, reinforces, supports

Dense line retards surface water flow

Dry, slope <45, erodible, cut slope

2 seasons

Thin line easily broken

Diagonal line grass planting

Catches, reinforces, some support

Dense line guides water along the line

Wet, permeable, fine, cut slopes

2 seasons

Rills break through

Grass seeding


Dense grass, mat, rooting system

Consolidated debris slopes <45

3 seasons

Can cause liquefaction, young plants get washed away or dried

Palisades


Dense line above and below the ground retards surface and shallow water flow

Slope <30, dry, erodible and consolidated debris

2 seasons

Causes small slumps, requires many cuttings, high mortality

Brush layering


Dense line, strong buried branches retard surface and shallow ground water flow

Slope <45, dry, erodible and consolidated debris

One season if planted early and watered

Destructive to slopes during the excavation, requires many cuttings

Fascines

Catches, supports, drains

Woody bundle, dense stems, porous, can drain soil if laid down slope

Consolidated debris slopes, <45

3 seasons

Destructive to slopes, requires many cuttings, slow to develop, high mortality

Shrub planting

Transpires, catches, armours, reinforces, anchors, supports

Bunchy leaves, multiple stems, lateral roots, root cylinder, tap roots

Any slopes < 45.

At least 4 seasons

Tree planting

Transpires, armours, reinforces, anchors, supports

Lateral and near vertical rooting systems, root cylinder

Any debris slopes <45, gully side slopes

At least 5 seasons

Top heavy on steep slopes, leaf drip, canopy shades smaller plants

Bamboo planting

Transpires, catches, armours, reinforces, supports

Dense poles, massive rooting systems, dense leaves, grows all year

Slope <30, base of slope, erodible slopes, preferably wet places

At least 5 seasons

Source plant damage, delicate, requires nursery space, heavy to transport

79



CHAPTER : 07 SMALL SCALE OF CIVIL ENGINEERING SYSTEMS

INTRODUCTION To solve the problems on slopes different types of civil engineering structures can be considered in bioengineering. Only the small-scale civil engineering structures are taken into account. Some of such small-scale structures are as follows.                  

Wattle fence Checkdam Jute net Wire netting Wire fence Rendering Revetment wall Slope cover Dentition Stone pitch Prop wall Bolster Toe wall French drain Unbound masonry ditch Bound masonry ditch Unlined earth ditch Bound masonry ditch

80



CIVIL ENGINEERING STRUCTURES

Wattle Fence

81



Gabion panel placing Gabion panel filled with stonesWooden peg

Figure: Bolster Construction

check dam

French Drain

82



The main civil engineering structures used for slope stabilization and erosion control in conjunction with bio-engineering are as follows: a. Toe wall: - Toe walls are constructed to protect the base of a slope from undermining or other damage, such as grazing by animals. b. Retaining wall: - Retaining wall is wall built to resist the pressure of earth filling or backing, deposited behind it after it is built. The main function of the wall is to support the slope. It also prevents the toe cutting. c. Dentition wall: - It any structure constructed on the slope where there are small fissures, patches. Its main function is to armour. d. Prop wall: - It is structure constructed where there is underlying of soft and hard rock. It is used to prevent differential weathering of soft rock and to support hard rock. e. Check dam: - Check dam are constructed to prevent the down-cutting of runoff water in gullies. They ease the gradient of the gully bed by providing periodic steps of fully strengthened material. f. Wire bolsters: - Wire bolsters cylinders are laid in shallow trenches across the slope. They prevent surface scour and gullying by reinforcing and fulfilling intermittent armouring functions and provide shallow support. g. Stone pitching: - Stone pitching is used to armour a slope. This gives a strong covering. It is freely drained and will withstand considerable water velocity. h. Surface and Subsurface drains: - Surface drains are used to remove surface water quickly and efficiently. Surface drains include horizontal drain, cascade, etc. And the subsurface drains are used to remove ground water quickly and efficiently. These are usually restricted to civil engineering structures. i. Jute netting: - A locally made geo-textile of woven jute netting is placed on the slope. It has three main functions. i. Protection of the surface allowing seed to hold and germinate. ii. Improvement of the microclimate on the slope surface by holding moisture and increasing infiltration. iii. As it decays, to act as mulch for the vegetation established. j. Wattle fence: - Low fence of bamboo or other plant material are built along the contour to trap debris moving down the slope and to prevent surface scour are known as wattle fence. After a certain period, terrace is formed. Jute Netting Materials and equipment: woven jute netting; hardwood cutting from shrub or tree, 2 to 5 cm in diameter and 30 to 40 cm. long; 83

CIVIL ENGINEERING IV/I tools for cutting wood and jute; iron bar for making hole; and wooden mallet.


Method: a trim to an even slope : make sure there are no small protrusions or depressions which will interfere with the netting, remove protruding rocks if possible; b peg the netting : starting at one end of site, peg the end of one roll of netting 30 cm above the slope to be covered; c

slowly unroll the netting down the slope;

d

peg the netting: allowing some slack in the netting, begin to peg it from the bottom of the slope. Hammer hardwood cuttings or pegs through it at intervals of 50 to 100 cm leaving the cuttings protruding about 8 cm. While working on the slope never hang on the netting - always stand on the pegs;

e

cover the whole slope with netting : repeat the process, making sure that the vertical edges of the net meet, until the whole slope is covered in netting;

f

butt joint the strips : place a series of pegs down each side of the butt joint so that the jute is held together as a continuous net;

g

Carefully adjust the netting : if necessary adjust the netting in order to reduce the tension and let it hug the surface closely. If it remains tight it will not lie right against the slope surface;

h

place additional pegs : add further pegs as necessary to ensure complete surface contact;

i

trim lower edges : cut the netting strips to the length required.

Advantages: it provides rapid cover for the slope surface; even on the harshest sites the young seedlings are protected from run-off and drought untilthey become established; jute netting is easily produced locally. Disadvantages: it can only be used in limited places because it has a high moisture holding capacity; netting has a short life span unless it is bituminised, and even then it will last for no more than 3 years. Gabion Wire Bolsters Gabion bolster panels are normally 5 m x 1 m. Where larger bolsters are required 5 m x 2 m panels can be woven. They are made on a conventional gabion-weaving frame but with a much smaller mesh than usual. Heavy coated 10 swg wire is used for the border and 12 swg for the mesh. Materials and equipment: woven gabion panels; 84

CIVIL ENGINEERING BIOENGINEERING IV/I Gabion Wire Bolsters 12 mm mild steel rod cut into 2 m lengths; boulders; tools for digging trenches and for working with gabion wire; and hammers.

PREPARED BY: DKB

Method: a trim the slope : first trim the slope to be treated to an even slope with no small protrusions or depressions, which will interfere with the bolsters. Remove protruding rocks if possible; b

mark out a contour : starting about 2 metres from the bottom of the slope, mark out a contour line across the slope with the aid of a spirit level;

c

dig a trench along the line : the trench should be about 30 cm wide and 30 cm deep;

d

lay a gabion bolster panel lengthways along the trench : make sure the edge of the panel on the lower side is flush with the edge of the trench;

e

fill the bolster with stones larger than the mesh size;

f

fold the upper edge of panel over the stones and join it to the lower panel edge. Leave a 10 cm flap from the upper edge extending over the lower edge;

g

join abutting bolsters across lope : form the bolsters into a continuous line across the slope and close the extreme ends with wire;

h

backfill: backfill the material around the bolsters, compact it and clean away surplus debris;

i

peg with steel bars: drive mild steel bars into the ground at right angles to the slope every 2 metres along the bolsters. Position them immediately below and touching the bolsters, and drive them in far enough so that they cannot be pulled out by hand;

j

cover remaining site: repeat steps 'b' to 'i' 2 m higher up the slope and repeat again until the area is covered;

k

starting from the top of the slope, clean away surplus debris and make sure that backfill is complete and firm.

Advantages: provide very strong and durable surface scour checks; stronger and longer-lasting than wattle fences; and freely drained and so little moisture is accumulated on the slope. Disadvantages: relatively expensive to install; and contour bolsters give rise to an increase of infiltration, which can cause slumping on some slopes.

85

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB Key Features of Small Check Dams Check dams are often poorly constructed and either fail or require remedial work. You should give attention to the following points:     

build sound foundations on a good base; key dam well into gully sides; include weep holes to drain water from behind wall and reduce hydrostatic pressure; make a notch and slope top of dam towards centre so water does not scour sides; point top of wall with cement mortar; and shape to get counterbalance moment.

CIVIL ENGINEERING WORKS An appropriate type of a small-scale structure depends upon their function and site requirement including position to stabilize. The following table explains the functions, applications, life span and limitations of a few small-scale structures. Function

Application

Position

Life span

Catch Wattle fence

Cheap easy to Mid slope 1 season install

Site requiremen ts

Limitations

Stakes can Weak be driven Undermining Very small amount of material

Jute net

Cheap

Unbitumin ised

Sandy soil

Top & 1-2 mid slope seasons

Smooth plane slope Homogeneo us materials

> 300 slope

Shrinks Not on fine plastic soils Not on cobble size soil Cannot be riling soil

Bituminise d

Sandy soil > 300 slope

Top & 5 years + mid slope

Jute netting Wire netting

Hard rock slope

Up & mid 20 years + slope

Wire fence

> 300 slope

Mid slope 10 – years

86

used

in

Smooth plane slope

Weak, light in weight and requires many pegs

Homogeneo us materials

Small amount & size of material

Stakes can Not on fine plastic soils be driven Not on cobble size soil

20 Good foundation

Cannot be used in riling soil Expensive


BIOENGINEERING PREPARED BY: DKB Difficult to install Not on soft rock

Checkdam

Small gullies

Gullies Mid down slope

25 years + &

Need to be Expensive well keyed Small amounts retained

Armour Slope cover

Permeable slope Any slope

Top & mid slope

1–3 seasons

Temporary measure Wind damage Installation difficult for large area Damaged by debris & swift water

Stone pitching

Erodible soil slope

River banks

25 years +

Gully base & floor Rendering

Non-weatherable fractured rock

Usually at 25 years + toe

Smooth face No resistance to any stress

Coarse consolidated material Up to 900 slope Revetment wall

Debris slope

25 years +

> 500 slope

Foundation needed Space needed for shape

Dentition

Alternate rock slope

Usually mid slope

25 years +

300 - > 500 slope

87

CIVIL ENGINEERING IV/I Homogeneous slope

Function

Application


Position

Life span

Site requirement s

Limitations

Support Toe wall

Debris slope

Base

25 years +

Bolster

Debris slope

Mid slope 25 years +

Up to 500 slope

Required shape

Mass movement < 250mm

Not too coarse & rocky soil

Can be undetermined

Specialized skills & materials Prop wall

Alternate rock layers

Mid slope 25 years +

Irregular shape

Drain Unlined earth ditch

Consolidated debris

Foundation bed

Mass movement < 250mm

Hard bed not too fractured

Top slope

Impermeabl e soil

Easily evoked

Must be neatly built

Easily damaged

Good foundation

Non flexible

Slope > 150 Unbound masonry drain

Consolidated debris

Bound masonry drain

Consolidated debris

Slope < 50

Slope < 50

Any

25 years + in theory

0

Any

25 years +

0

88

Cracks & leaks

CIVIL ENGINEERING IV/I French Consolidated drain debris (surface Wet sites gravel drain) (ground water

BIOENGINEERING Any

25 years +

PREPARED BY: DKB Maximum depth 2m Difficult to install when depth > 1m Expensive

and surface water) Slope < 500

INTERACTION BETWEEN PLANTS AND CIVIL ENGINEERING STRUCTURES In slope stabilisation we may have a choice whether to use: -civil engineering on its own; -vegetative engineering alone; -

a combination of the two.

As soil conservation officers, we need to understand the principles underlying the relationship between vegetative engineering systems and civil engineering systems.

RELATIVE STRENGTH OF STRUCTURES OVER TIME. The strength of a structure at different stages of its life can be related to its maximum strength. This can be described as a percentage of the maximum strength.

89



Life span of vegetative structures

100 %

80 Relative

60 strength

40 of

20 structure

0 0

1

2

3 Years

90

4

5

6

7



Life span of small civil engineering structures 100 %

80 Relative

60 strength

40 of

20 structure

0 0

1

2

3

4

Years

91

5

6

7



Combined life span.

% of Relative Strength of Structure

100  Vegetation System

80  Civil Engineering Structures

40 0

1

2

3

4

5

Year 20

From above graph we can conclude that the civil engineering system get its early strength but as the time elapses, reduces its strength. At the same time when we use bio engineering system properly the strength increases up to limit although early strength is zero. Combined life span: As the relative strength of engineering structures decreases, the relative strength of plant structures 0 increases. Note that these graphs relate to the performance of each type of structure separately. They do not compare the actual strength of the civil engineering structures compared with the strength of the vegetative engineering structures.

Jute net and grass can both be used to perform a catching function. In the beginning the fine soil retaining capacity of the jute net is very high and each small square behaves as mini check dam. With time the jute decays which weakens the net and consequently its soil retaining capacity decreases. Ultimately the net will fail to carry out any retaining function. The grass slips grow up with time and start to retain soil on the slope due to the development of root and shoot systems. When grass is fully grown, it stays at 100% relative strength. As the relative strength of the jute net declines the relative strength of the grass increases. The soil retaining function of the jute net is handed over to the grass.

92

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB Physical relationships between civil and vegetative engineering structures: Various relationships may exist between the functions of civil and vegetative engineering structures, e.g.: -

toe wall below bamboo-

structure protects plant;

-

plants around end of toe wall -

plant protects structure;

-

trees above toe wall -

plant improves performance of structure;

-

fence with young plants below - plant replaces structure.

These are the four ways in which civil and vegetative engineering structures can be used together.

Compatibility of engineering structures: In the last example the function of the civil engineering, structure is handed over to the plants. If this is to happen the engineering functions of the two structures must be the same.

93



CHAPTER : 08 OPTIMAL TECHNIQUE SELECTION OF OPTIMAL TECHNIQUE Choice of stabilisation techniques Choosing stabilisation techniques is a complicated process, which is not fully understood. There are many variables, most of which cannot be measured in the field. These notes give a practical analysis to reach an optimum course of action. Do not consider this information definitive. Always remember the most important part of the analysis is attention to detail. EROSION PROCESSES ACTIVE ON SITE First look at the site and its surroundings. There is no such thing as a simple ‘text book’ landslide. Each site has a variety of processes at work. You must identify them before you start any remedial work. The site may contain one or more type of erosion such as: - surface erosion, such as rilling and gullying; - planer slide, on a shallow slip plane parallel to the surface (translational landslide); - shear failure, on a deep, curved slip plane (rotational failure); - slumping of material when very wet, through low particle cohesion; - falling of debris due to failure of the supporting material. Secondly, there are both ‘internal’ and ‘external’ factors affecting the site. These include: -

Internal factors: small fault lines causing differential erosion in parts of the site; small slip planes additional to the main failure mechanism; seasonal springs within the site;

-

External factors: gullies which may discharge on to the site; landslides which may supply debris on to the site; rivers which may undercut the toe.

The next stage involves establishing whether the cycle of erosion has reached a stage at which it can be stabilised. If it has not, leave the site until after the next monsoon and do not carry out any further work at this stage.

94



INITIAL ASSESSMENT OF TREATMENT NEEDS If it looks as if stabilisation of the site is feasible, you can continue the process of decision making. A further series of questions given below helps to simplify the problems. Action if the answer is yes

Question Is the site very long, steep and in danger of a massive failure below the surface?

Use retaining walls to break the slope into smaller, more stable lengths.

Is the foot of the slope undermined, threatening the whole slope above?

Consider building toe walls.

Is there a distinct overhang or are there large boulders supported by a soft, eroding band?

Consider building prop walls.

Is the slope made up mostly of hard rock, so that planting nursery stock would be impossible?

Consider direct seeding as an option.

Is the slope rough, covered in loose debris or does it It must be trimmed. have any locally very steep or overhanging sections, however small?

Slope segments Once you have answered these questions, you can move on to a more detailed examination of the slope segments. A slope segment can be defined as a length of slope with a uniform angle and homogeneous material that is likely to erode in a uniform manner. The most straightforward way to approach the choice of stabilization technique is to split sites into segments of slopes. The assumption is that each segment can be treated using the same technique or techniques. But first, there are two important questions to answer.

Question

Action if answer is yes

Is the slope segment longer than 15 metres?

There may be a risk of serious surface erosion. Therefore some kind of physical scour check should be used, such as wire bolsters.

Is the slope made up of poorly drained

There is a danger of shallow slumping. Techniques used on this sort of material must be designed to 95

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB material, with a relatively high clay content? drain rather than accumulate moisture. Guidelines for applying bioengineering techniques The diagram entitled ‘Guidelines for applying bioengineering techniques to all slopes’, is an attempt to define the techniques to be used on different sites. Many factors determine the optimum technique or combination of techniques, but only the most important have been included here for the sake of simplicity. The following notes explain the five columns. Slope angle This is the primary distinction, as it is used to identify the sites which need only mild soil conservation treatment, i.e., those less than 30o. A slope steeper than 45o has seriously steep angle and will present greater erosion problems. Slope length The length of 15 metres is partly arbitrary but represents a good dividing figure between ‘big’ and ‘small’ sites. Slope segments longer than 15 metres are open to greater risks in terms of both gullying and deep-seated failures. Aspect Aspect is the orientation of a site relative to the sun. In fact, this category relates to more than just aspect. It covers the environmental dryness of each individual site. The entire site moisture regime must be considered, although aspect is often the dominant factor in determining the site moisture. Other major factors are: -

Altitude; Rain shadow effect; Topographical location; Stoniness; Soil moisture holding capacity; and Winds and ex-monsoon rains.

Material drainage This column relates to the internal porosity of soils and the likelihood of their reaching saturation and losing cohesion, thereby starting to flow. Those materials, which have poor internal drainage, tend to have high content of clay relative to sand and silt in the fine fraction. They tend to be prone to shallow slumping if too much moisture accumulates. Stabilisation requires some kind of drainage in addition to protection. Optimal techniques One or more techniques are given which are known to be successful on general sites of each type. However, the general picture may not cover every case and so this flow chart cannot be considered fully comprehensive. Some local variations may be needed, the engineer needs to determine this on site.

96



GUIDELINES FOR SELECTION OF OPTIMAL TECHNIQUES Slope angle START 

Slope length 

>15 metres

Aspect 

Material drainage 

Optimal technique 

N, NE (NW,E)

Good

Diagonal grass lines

S, SW (SE,W)

Good

Contour grass lines

N, NE (NW,E)

Poor

1 Downslope grass lines and strengthened rills or 2 Chevron grass lines and strengthened rills

>450 <15 metres

S, SW (SE,W)

Poor

Diagonal grass lines

Any

Good

Jute netting and planted grass

N, NE (NW,E)

Poor

1 Downslope grass lines or 2 Diagonal grass lines 1 Jute netting and planted grass or

S,SW (SE,W)

Poor

2 Contour grass lines or 3 Diagonal grass lines

>15 metres

1 Horizontal bolster cylinders and tree planting or

Good

2 Downslope grass lines and strengthened rills or

Any

3 Grass seeding, mulch and wide mesh jute netting Poor

Herringbone bolster cylinders and tree planting

30—450

1 Brush layering with woody cutting or Good

2 Contour grass lines or 97

CIVIL ENGINEERING IV/I <15

BIOENGINEERING PREPARED BY: DKB 3 Grass seeding, mulch and wide mesh jute netting

Any

metres

Poor

1 Diagonal grass lines or 2 Herringbone fascines and tree planting or 3 Herringbone bolster cylinders and tree planting

<300

Any

Good

1 Contour strips of grass and trees or

Any

2 Tree planting Poor

1 Diagonal lines of grass and trees or 2 Tree planting

Any

Any

Any rocky material

Direct seeding of shrubs or small trees

Notes: 'Any rocky material' is defined as material into which rooted plants cannot be planted but seeds can be inserted in holes made with a steel bar. A chevron pattern is like this: <<<<< A herringbone pattern is like this:  (like the bones of a fish)

98



CHAPTER : 09 NURSERY What is a nursery: It is a factory that produces the plant and plant materials of required quality when required, how much required and at an affordable cost. Main Component of the Nursery: General: Compound wall or fence Office: Chowkidar’s hut, Vehicle access, working area, path ways Storage: store for soil, sand, Compost, Pesticide Water: Water tank and accessories , Drainage system Beds: Seed bed, Stool cutting , Bare root plant , Grass, Bamboo, Standout bed for polypot , shades for bed . MATERIAL CHECKLIST:  Soil, sand, seed  Compost fertilizer  Fungicide, insecticide  Heavy gauge poly bags for storage  Shed material (bamboo, hessian)  Wire, nails, string, wire mesh  Seed bed level  Pen, pencil  Poly pot 4” *7”  Heavy gauge polythene sheeting  Water proof marker, register, soap etc. EQUIMENT CHECKLIST  Kuto, Kodalo, Kodali  Chhupi  Hasia, Khukuri  Khanti, Shovel 99

CIVIL ENGINEERING IV/I  Secateur/Scissors


 Tin trunk with padlock  tray  Measuring tape  Doko  Watering can  Flit gun sprayer  paper punch  Plant carrying tray  First aid kit  Safety equipment kit  Soil and sand sieves

Factors to be considered for the selection of a nursery site:  The number of plants of each species to be produced each year;  The type and size of plants;  The location of the planting sites to be supplied;  The expected life of the nursery.  The site is chosen at least six months before the first seed is to be sown. Land ownership  As far as possible, the nursery should be established in own land;  Legal provisions should be carried out for the rented land. Water supply  A guaranteed supply of 1,000 litres (1 m3) of water per day is needed for a nursery of 20,000 plants watered with a watering can. Surface irrigation requires considerably more.  The water right should be registered in the water resource committee.

100

CIVIL ENGINEERING IV/I General location:


1. The site should be as close as possible to the centre of the area to which plants will be supplied and near to the road. 2. Aspect is very important. North facing slopes are cooler and more humid and are better for nurseries at lower elevations, whereas nurseries above 1200 m are better on warmer southern slopes 3. A slope of 2-3 % is necessary to allow water to drain off without causing erosion. Availability of materials and labour: 1. Deep loamy soil, if possible with good content of organic matter (2 %), on a well-drained site. 2. A nursery with a target of 20,000 usable plants would fill 25,000 pots. For (4" – 7") pots, this would require 12.25 m3 of potting mixture. For a 2:1:1 soil:sand:compost mixture ,about 6.2 m3 of soil and 3.1 m3 of sand are required. 3. It should be near to the peoples’ access so that they could go to work and come back to their place in the evening. SPACING NURSERIES:  Nurseries should be established at intervals according to need.  Each climatic area where work is to be carried out should be represented by at least one nursery;  Ideally plants are produced in a nursery immediately next to their eventual destination although this cannot be achieved in every case. On some mountain roads crossing much unstable terrain and a wide variety of climatic zones, one nursery per 10 km may be necessary. Elsewhere a distance of 25 km between nurseries may be adequate. Nurseries need to be as close as possible to the sites they will serve.  The location must be technically suitable.  The final selection should be based on evaluating the relative advantages, and disadvantages of three or more possible sites.  Permanent nurseries with a production capacity of less than 100,000 grass slips, or 25,000 shrub or tree seedlings, are not usually economically viable  Small nurseries can be better than one large one 101

CIVIL ENGINEERING IV/I Advantages of a small nursery:


 the risk is spread during the planting season: blockages of the road which disrupt transport are less likely to jeopardise the planting programme;  the dangers of drought, disease or poor management in one nursery will affect only part of the total stock;  transport of stock from nursery to site is minimised which saves money and reduces stress damage to the plants;  nurseries in each climatic zone allow a wider range of plants to be produced;  each nursery requires a trained foremen (Naike), this allows a greater transfer of skills which is a development objective;  nurseries act as a focus for work in the local community.

TYPES OF BEDS:  Grass Slip bed  Beds for sowing tree or shrub seeds  Stand out beds for polypots  Beds for bare root seedling and stumps  Stool beds for cutting  Beds for bamboo culm cutting

102



NUMBER OF PLANTS PER PLANTING DRILL Rhizome

1/ drill

Amliso, Nigalo etc.

Grass slip

2/drill

Babio, Kans etc.

Stem cutting

1/dril

Napier, narkat etc

Stolon

1 or 2/drill

Dubo

Calculation of Nursery Area:  Calculate the required space to produce o 500,000 grass slips o 18,000 shrub/tree plants in 4”*7” polypot Nursery altitude Terai to 1200 m

Species Amliso Any other grasses

Above 1200 m

Any grasses

Slips first planted February February April/May February/March

Number to plant Final site number/3 Final site number/7 Final site number/3 Final site number/3

Calculation of the space for grass bed:  Divide the required number of slips by number of plants to be developed in nursery from a slip ( here 5)  500000/5=100000  Divide it by the number of plants to be planted in 1 m2 ( here 100)  100000/100=1000 m2 Calculation of the space for tree/shrub seedlings:  Add 25% to the required number  18000+25% of 18000=22500  Divide it by the number of plants that can accommodate in 1 m2 (here 128nos.)  22500/128=176 m2  Add 50% to this area for stocking and respacing  176+88=264 m2 TOTAL LAND REQUIRED: Add all required land area 103

CIVIL ENGINEERING IV/I  1000+264=1264 m2


 Add space for seed bed, bamboo bed if required.  Multiply it by 1.5 if the land is unterraced and by 3 if it is terraced  DESIGN REQUIREMENTS OF THE PHYSICAL COMPONENTS OF NURSERIES Compound wall or fence Nursery store, Office and Chaukidar’s hut Other structures Water supply Drainage Nursery beds Pathways Other

Component

Design features

Reasons for design

Compound wall or fence

Secure against all animals Strong and long lasting Built using local materials Simple but effective gate

To protect the nursery adequately As cheap as possible Effective Show people it is private

Nursery store/ office/ Chowkidar's hut

Secure against all unwelcome people Strong and long lasting Big enough for all its functions Built suing local materials Good quality so the chowkidar will be happy to stay there Efficient layout

To look after tools, seeds, etc. safely To give the chowkidar a reasonable place to stay As cheap as possible to be effective

104



Vehicle access and turning area

Beside safest and easiest road access point Adequate space for turning and unloading (if space is limited, vehicles may reverse in)

Easy transport of goods in and out of the nursery

Soil/sand store

Adequate size for storing all soil and sand Space for working in during set weather (optional)

As cheap as possible to be effective

Working area

Big enough for all operations Big enough for more labourers to work in at peak times Hard, well drained surface If possible, shaded by a large tree

To enable efficient performance of all operations

Water tank accessories

and

At highest part of nursery Permanent good water source Well built tank Tank of large capacity Good taps Hose pipes reaching every bed in the nursery

105

Water is most essential for plants It must be guaranteed at all times of the year Water must be easily available in all parts of nursery



Drainage system

Must prevent erosion in the nursery Must prevent erosion in the nursery Keep paths and working areas hard and dry

To keep the nursery in good condition all year round As cheap as possible to be effective

Pathways to all parts of the nursery

Well made so they last a long time Drained so they are good during rains

To allow easy access As cheap as possible to be effective

Compost bays

Strong and long lasting Big enough for all the nursery's needs Built using local materials

To provide compost for the nursery on an annual basis As cheap as possible to be effective

106



CHAPTER:10 MANAGEMENT INTRODUCTION Bioengineering programming work is very important as the activities directly depend on the seasonal characteristics. In the other hand financial obligation regulates the implementation of the work. The HMG/N financial system is clear that the fiscal year starts from Shrawan which is the prime time for bioengineering activities. Every institution must have a system, which regulates its expenditure. However, often it seems to hinder technical operations. We must know how to work within the system if we are to carry out bioengineering works effectively. A better programming ensures efficiency, effectiveness and economy by utilizing scarce resources as minimum as possible and by producing as more output as possible. Programming is the advance planning. Scheduling is an important task in the process of programming. There are various types of schedules. Some of them are: - Construction schedule - Equipment schedule - Material schedule - Labour schedule - Financial schedule CONSTRUCTION SCHEDULE Before preparing a construction schedule various operations involved in the construction project like estimation of quantity, abstract of cost etc. are to be calculated. It shows the clear picture of the project. An example of construction schedule is given below: Project No. … Year …….

Name of the Project ……………….

S. No .

Activities

Quantity

Unit

Location ……….

Rate per week

Total time required

Baishakh 1

e

107

2

a

e

3

a

e

4

a

e

a


note: e = estimated


a= actual

EQUIPMENT SCHEDULE It shows the complete list of equipment required for the project on different dates and also their duration. It helps planning the equipment required for the project in advance. Project No.

Year …….

Name of the Project:

Location ………...

S. No.

Equipment

1

bulldozer

Total nos. Required

Baishakh 1

2

3

Jestha 4

1

2

3

Ashadh 4

1

2

3

4

MATERIAL SCHEDULE In order to deliver materials to the site well in advance and not far in advance or delaying material schedule is prepared. Project No.

Year:

Name of the project:

Location:

S No .

Description of materials Total quantity

Baishakh 1

108

2

3

Jestha 4

1

2

3

Ashadh 4

1

2

3

4

CIVIL ENGINEERING IV/I 1 Cement


LABOUR SCHEDULE On the basis of construction schedule labour schedule is prepared. It shows the required types of labour, their numbers and period of involvement. Project No. Year:


Location:

S. No .

Classification of labours

1

Carpenters

Total nos.

Baishakh 1

2

3

Jestha 4

1

2

3

Ashadh 4

1

2

3

4

FINANCIAL SCHEDULE It is important to prepare the financial schedule for the proper planning of the financial activities. In the absence of the schedule there will be the dilemma of both the expenditures and receipt. As per the budget allocation practice in Nepal, the whole budget for the year is disbursed in three four monthly segments. The financial programming, hence, has to be prepared accordingly. FINANCIAL PROGRAMMING AS PER BUDGET ALLOCATION Project No.

Year:


Location:

S. No.

Particulars

Total Quantity

Total Amount

Work for the Year Q A %

109

I

II

III

Q A % Q A %Q A %

Remar ks



FINANCIAL PROGRAMMING AS PER EXPENDITURE REQUIREMENT Project No.

Year:


Location:

Week after starting

Construction Activities

Expenditure per week

Cumulative Expenditure

Remarks

BAR CHART It is a simple and easily understood tool used for construction planning and controlling. It is a graphical representation of various activities showing the duration, starting and the completion dates of the construction projects. On a chart by means of the horizontal bars different activities are represented. The length of each bar indicates the duration required for the completion of the operation. By using an extra dark bar parallel to the bar already shown on the chart progress of the activity also can be noted down.

An example of a bar chart for construction of Check dams in a gully

S. No.

Description of work

Baishakh 1

2

3

Jestha 4

110

1

2

Aashadh 3

4

1

2

3

Shrawan 4

1

2

3

4

CIVIL ENGINEERING IV/I 1 Site Clearance

2


Earth Work in Excavation

3 Random Rubble Masonry 4 Bio Engineering Activities

111



BIOENGINEERING PROGRAMMING WORKS ( ANNUAL CALENDAR) Month

Main activities

Comments/other works

Shrawan Site plantation works: all grass slips and seedlings; all shrub and tree seedlings and hardwood cutting; all remaining direct Jul-Aug seeding

Site plantation starts this month in the Mid and Far Western Regions

Observation of newly planted sites and maintenance as required Bhadra AugSep Aswin Sep-Oct

Observation of newly planted sites and maintenance as required

Budget release expected now; start detailed programming


Jute net weaving takes place all year round but timely ordering ensures the best quality fibres and lower prices

Conduct post-monsoon survey of roadside slopes, prioritise problem areas and begin planning for remedial works Make initial assessment and order for jute netting (jute harvesting season) Carry out coppicing and pollarding of large trees Kartik NovNov

Preparation for seed collection: final establishment of quantities required and planning of seed sources Compost and mulch making

Mangsir

Seed collection, treatment and storage

NovDec

Preparation for physical site works; planning, programming, contracting etc. Compost and mulch making

Poush

Seed collection, treatment and storage

Dec-Jan

Begin to prepare nurseries for operations in the spring Preparation for physical site works; planning, programming, contracting, etc.

Magh

Preparation of nurseries for operations in the spring

Jan-Feb

Low altitude nurseries start seed sowing Site works : slope trimming, start of construction of civil 112

This is the main seed collection period for grasses and some shrubs and trees, but the seeds of some species ripen at other times Existing nurseries should be in good order all year round but will still require beds to be cultivated, polypots to be filled, etc.

CIVIL ENGINEERING IV/I works, etc.


Seed collection, treatment and storage Carry out pruning and thinning of large trees Phalgun

Main period for starting nursery production

Feb-Mar Sowing of seeds Site works : slope trimming, civil works construction, etc. Carry out pruning and thinning of large trees Chaitra

Nursery operations in full swing

MarApr

Site works: slope trimming, civil works construction, etc.

Baishak h

Nursery operations in full swing Site works: slope trimming, civil works construction, etc.

AprMay

Application of jute netting on site

Jestha


MayJun

Final physical site works Final preparation of materials for site planting Direct sowing of shrub and tree seeds on site Direct sowing of grass seeds on gentle slopes or under mulch

Ashadh

Nursery operations continue

Jun-Jul

Site plantation works: all grass slips and seedlings; all shrub and tree seedlings and hardwood cuttings; all remaining direct seeding

113

Site plantation works start this month in most parts of the Eastern, Central and Western Regions



BIO-ENGINEERING: GENERAL WORKS ANNUAL PROGRAMME FISCAL YEAR: No Work activity

Shrawa Bhadra Aswin Kartik Mangsi Poush n r

1 Complete 2057/58 site planting 2 Seed collection: grasses other species 3 Seed treatment 4 Seed storage 5 Site assessment 6 Planning civil/site preparation works 7 Tendering contracts

and

arranging

8 Implementing civil works 9 Planning bio-engineering needs 10 Bio-eng stock production 11 Final site preparation

114

Magh Falgun Chaitr Baisha Jestha Ashad a k

CIVIL ENGINEERING IV/I 12 Placement of jute netting


13 Bio-engineering site works: grass seed sowing on site shrub seed sowing on site brush layering grass planting tree/shrub planting 14 Programming for FY ….. 15 Protection 16 Monitoring 17 Maintenance

115

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB The HMG/N financial system is clear and logical. Every institution must have a system, which regulates its expenditure. However, often it seems to hinder technical operations. We must know how to work within the system if we are to carry out bioengineering works effectively. RESTRICTIONS ON BIOENGINEERING WORKS IMPOSED BY THE NG FISCAL YEAR There are many difficulties for bioengineers and the main ones are those, which affect the annual programming of bioengineering works and the management of contracting. They are as follows:

the Fiscal Year ends in the middle of our main working period (i.e. the rainy season); unspent budgets are frozen; programmes have to be made well in advance and it may be difficult to alter them later; any changes in either the programme or the site location require a lot of file chasing in Kathmandu; at the end of the FY, there is much work to be done completing the accounts; this distracts from technical work; funds for the new FY are often not released by the Ministry of Finance for several months due to delays in approval of the work programmes by the National Planning Commission; the quotation system for employing local contractors is restricted by HMGN regulations; and civil engineering works are generally finished at the very last moment in the Fiscal Year, not leaving any time for bioengineering works. WAYS OF WORKING WITHIN THE NG SYSTEM TO REDUCE FINANCIAL PROBLEMS There are several ways of overcoming these problems. 1

2

3 4

If a budget has been proposed for bioengineering works in the Fiscal Year just started, up to one sixth of the annual budget may be used per month for the works. This needs to be requested by the Project Manager. If you are using contractors for the site works, contract packages can be arranged so that there is a defects and liabilities period of six or twelve months after the end of the Fiscal Year. If the contractor does not complete the works, then he will forfeit the retention money or performance bond. In exceptional cases, you can apply to the Director General for use of money from the Project's Deposit Account. In dire circumstances, you can apply for emergency funds (or again, from the Deposit Account). This would normally be for works resulting from a landslide or erosion of a serious nature, which has occurred unexpectedly during the monsoon, i.e. soon after the start of the new FY.

116



SUMMARY ANNUAL CALENDAR OF BIOENGINEERING WORKS Month

Main activities

Comments/other works

Shrawa n

Site plantation works: all grass slips and seedlings; all shrub and tree seedlings and hardwood cutting; all remaining direct seeding

Site plantation starts this month in the Mid and Far Western Regions

Jul-Aug

Observation of newly planted sites and maintenance as required Bhadra AugSep Aswin Sep-Oct


Budget release expected now; start detailed programming


Jute net weaving takes place all year round but timely ordering ensures the best quality fibres and lower prices

Conduct post-monsoon survey of roadside slopes, prioritise problem areas and begin planning for remedial works Make initial assessment and order for jute netting (jute harvesting season) Carry out coppicing and pollarding of large trees Kartik NovNov Mangsi r NovDec

Poush

Preparation for seed collection: final establishment of quantities required and planning of seed sources Compost and mulch making Seed collection, treatment and storage Preparation for physical site works; planning, programming, contracting etc. Compost and mulch making Seed collection, treatment and storage

Dec-Jan Begin to prepare nurseries for operations in the spring Preparation for physical site works; planning, programming, contracting, etc. Magh

Preparation of nurseries for operations in the spring

117

This is the main seed collection period for grasses and some shrubs and trees, but the seeds of some species ripen at other times Existing nurseries should be in good order all year round but will still require beds to be cultivated, polypots to be filled, etc.

CIVIL ENGINEERING BIOENGINEERING IV/I Jan-Feb Low altitude nurseries start seed sowing

PREPARED BY: DKB

Site works : slope trimming, start of construction of civil works, etc. Seed collection, treatment and storage Carry out pruning and thinning of large trees Phalgun Main period for starting nursery production FebMar

Sowing of seeds Site works : slope trimming, civil works construction, etc. Carry out pruning and thinning of large trees

Chaitra


MarApr

Site works: slope trimming, civil works construction, etc.

Baishak Nursery operations in full swing h Site works: slope trimming, civil works construction, Apretc. May Application of jute netting on site Jestha


MayJun

Final physical site works Final preparation of materials for site planting Direct sowing of shrub and tree seeds on site Direct sowing of grass seeds on gentle slopes or under mulch

Ashadh

Nursery operations continue

Jun-Jul

Site plantation works: all grass slips and seedlings; all shrub and tree seedlings and hardwood cuttings; all remaining direct seeding

118

Site plantation works start this month in most parts of the Eastern, Central and Western Regions

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB BIOENGINEERING: GENERAL WORKS ANNUAL PROGRAMME No

Work activity

FISCAL YEAR : 2056/57 Shrawa n

1

Complete 2051/52 site planting

2

Seed collection: grass other species

3

Seed treatment

4

Seed storage

5

Site assessment

6

Planning vivil/site preparation works

7

Tendering and arranging contracts

8

Implementing civil/preparation works

9

Planning bioengineering needs

10

Bio-eng stock production (in nursery)

11

Final site preparation

Bhadr Aswi a n

Karti k

119

Mangs ir

Poush Magh

Phalgu n

Chaitr a

Baishak Jesth Ashadh h a

CIVIL ENGINEERING IV/I 12 Placement of jute netting 13


Bioengineering site works; grass seed sowing on site shrub seed sowing on site brush layering grass planting tree/shrub planting

14

Programming for FY 2053/54 Routine activities

15

Protection

16

Monitoring

17

Maintenance

120



BIOENGINEERING: LOW ALTITUDE NURSERY ANNUAL PROGRAMME No

Work activity

FISCAL YEAR : 2052/53 Shrawan

1

Bhadr Aswi a n

Karti k

Seed collection : grasses other species

2

Soil and sand collection

3

Compost : making turning

4

Purchase of polypots and other items

5

General preparation of nurseries

6

Polypot filling

7

Shade repairing

8

Grass tock :

plant out respace

9

Seedlings :

seed sowing

121

Mangs ir

Poush Magh

Phalgu n

Chaitr a

Baishak Jesth Ashadh h a

CIVIL ENGINEERING IV/I pricking out


respacing root pruning 10

Prepare stock to leave nursery Routine activities

12

Weeding

13

Protecting

14

General maintenance

122

CIVIL ENGINEERING BIOENGINEERING IV/I NURSERY ACTIVITY CALENDAR BY FISCAL YEAR

PREPARED BY: DKB

Activity Shra wan

Nursery consstruction

Bh ad ra

As wi n

Ka Ma Po rtik ngs us ir h

M a g h

Ph alg un

Ch aitr a

Bais Jes akh tha h

Complete by end of Mangsir

Soil and sand collection Order new supplies Making compost Turning compost

As required

Bed preparation Prepare potting mixes Filling polypots Check material sources Plant material collection Transplanting Re-spacing

As required

Check seed sources Seed collection

*

*

*

*

Seed treatment

*

*

*

*

Seed sowing Pricking out

As required

123

Ash adh

CIVIL ENGINEERING IV/I Root pruning

BIOENGINEERING PREPARED BY: DKB As required

Spacing out

As required

Weeding Maintain water supply Watering

As required

Shading of young plants

As required

Protection of the nursery Record keeping General maintenance

Regular checks and repairs made

Pest and disease control

Daily checks and action taken when necessary

Uplifting and preparing

As required

Transporting

As required

Site planting works

Depends on rain

Depends on rain

* Main seed collection period only; other seeds are collected at other times of the year.

This is an example only and a specific calendar must be made for every nursery. Bioengineering Norms and specificaton Rate analysis norms are standard formats that include the quantity of materials, numbers of different categories of labours required for completion of unit item of work. In order to standardize the analysis of rates for various items of work among various departments and offices, the norms are prepared and recommended by the government. Sequence of rate analysis norms forbio-engineering works Collection and preparation of seed

Collection

124

CIVIL ENGINEERING IV/I Collection of grass and hardwood

BIOENGINEERING PREPARED BY: DKB methods

cuttings for vegetative propagation Nursery operation and management (bed preparation)

Nursery operation

(seed sowing and transplanting; planting hardwood cuttings)

and management

Preparation of raised materials for extraction from the nursery compost and mulch production Direct seeding on site Planting grass cuttings on site Planting shrub and tree seedlings and cuttings on site

Bio- engineering

Vegetative palisade construction, brush layering and fascines Jute netting works

Small civil

Fabrication of gabion bolster cylinders

engineering

Bamboo tree guards

-

Tree guards

Example of specifications given in the'Work description' column Planting rooted grass slips on slopes 45 - 60º including preparation of slips on site. Operation includes digging planting hole to a max. of 5 cm depth with metal rod or hardwood peg, depending on nature of soil. The planting drills should be spaced 10 cm apart.

125

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB WORK NORMS FOR BIO-ENGINEERING WORKS OF RURAL ROADS For Hill Area S.

Respec tive

No .

Clause of Specifi cations

Description

18-1

Collection and preparation of seeds

61.

Unit

Unskill ed Labour (person day)

Skilled Labour (persond ay)

For Terai/Plain Area

Unskille d Labour (personda y)

a. Collection of grass seeds from sources within 1 km of the road, including separating and preparing seed for storage, and drying seed in the sun.

1 kg

1.50

1.50

b. Collection of large shrub seeds (e.g. bhujetro) from sources within 1 km of the road including seed preparation for storage after drying.

1 kg

0.45

0.45

c. Collection of medium-sized shrub seeds (e.g. 126

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Sealed bag = 1 no.

Khukuri

Khukuri

CIVIL ENGINEERING IV/I S.

Respec tive

No .


BIOENGINEERING PREPARED BY: DKB For Hill Area For Terai/Plain Area

Description

Unit


keraukose) from sources within 1 km of the road, including seed preparation for storage after drying.

d. Collection of medium-sized shrub and tree seeds (e.g. areri, khayer, ghobre and rani salla, sisau) from sources within 1 km of the road, including seed preparation for storage after drying.

e. Collection of small shrub and tree seeds (e.g. dhanyero, dhusun, tilka, utis) from sources within 1 km of the road, including seed preparation for storage after drying.



1 kg

0.75

0.75

1 kg

0.95

0.95

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) Sealed bag = 1 no.

Nanglo

Nanglo Sealed bag = 1 no.

1 kg

2.50

2.50

Nanglo Sealed bag = 1 no.

127



S.

Respec tive

No .


Description

18-2

Collection of grass and hardwood cuttings for vegetative propagation

62.

Unit


a. Collection of grass clumps (e.g. amliso, kans, khar) from sources within 1 km of the road, to make slips for multiplication in the nursery.

b. Collection of cuttings of small bamboos (e.g. padang bans, tite nigalo bans), suitable for traditional planting, from sources within 1 km of the road. Material minimum 10 cm of rooted rhizome and 90 cm of culm.

1000 slips

1.50



1.50

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Adequate supply of appropriate clumps.

Kodalo

Hessian jute = 5 m2

1000 nos.

3.00

3.00

Kodalo Adequate supply of appropriate

128

Khukuri


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) bamboos. Hessian jute = 10 m2

c. Collection of hardwood cuttings (e.g. assuro, bains, kanda phul, namdi phul, saruwa, simali) from sources within 1 km of the road. Material minimum 30 cm in length and 2 cm in diameter.

1000 nos.

0.85

0.85

Adequate supply of appropriate bushes. Hessian jute = 5 m2

129

Khukuri



S.

Respec tive

No .


Description

18-3

Nursery operation and management (bed preparation)

63.

Unit


5 m2

2.00


1.50


2.00

a. Construction of seed beds for tree seedlings, including materials for beds and shades. Bed is 1 m wide x 17 cm high and made up of: 5 cm of washed gravel, 5 cm of unsieved forest soil, 5 cm of 1:3 mix of sieved forest soil and washed sand, 2 cm of washed, sieved and sterilised sand.

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

1.50 Bamboo = 9 nos. Polythene = 9 m2

Khanti Shovel Pick axe Screen mesh

Bricks = 96 nos. Gravel = 0.25 m3

b. Construction of stand out beds for tree seedlings in polypots, including materials for

5 m2

6.00

6.00

Unsieved soil = 0.10 m3 Line string

130

Khanti


Respec tive

No .



Description

Unit




beds and shades. Bed is 100 cm wide x 15 cm high, with a 5 cm layer of gravel placed above the compacted ground.

c. Construction of beds for grass seeds, grass slips (i.e. vegetative propagation) and tree stool cuttings, including materials and hessian cover. Bed is 100 cm wide x 25 cm high and made up of: 5 cm of washed gravel placed above the ground, 5 cm of 1:1 mix of sieved soil and compost, and topped with 15 cm of 3:1 mix of sieved forest topsoil and washed sand.

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) = 13 m Binding wire = 3 kg

5 m2

1.50

1.00

1.50

Bamboo = 15 1.00 nos. Bricks = 96 nos. Gravel = 0.25 m3 Line string = 13 m Binding wire =

d. Construction of beds for propagation of 131

Shovel Pick axe

Shovel Pick axe


Respec tive

No .



Description

Unit


bamboo culm cuttings, including materials and hessian cover. Bed is 100 cm wide x 30 cm high. The ground below the bed is dug to a depth of 30 cm. Bed is made with 10 cm unsieved soil and 20 cm sieved soil. A bund 10 cm high is formed around the edge.



Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) 3 kg

5 m2

2.00

2.00

Shovel Gravel = 0.38 m3 Forest soil = 1.46 3 m Compost = 0.38 3 m Washed sand= 0.46 m3 Hessian cover = 10 m2

132

Pick axe Khukuri Log saw


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Gravel = 0.38 m3 Forest soil = 1.46 3 m Compost = 0.38 3 m Bamboo = 6 nos. Hessian cover = 25 m2

133



S.

Respec tive

No .


Description

18-4

Nursery operation and management (seed sowing and transplanting; planting hardwood cuttings)

64.

Unit


134



Skilled Labour (personda y)

Materials/

Equipment/ Tools

Royalties

Remarks


Respec tive

No .



Description

Unit


a. Tree seed sowing @ 10 g per m2 (mediumsized seeds) or 2 g per m2 (very fine seeds) into seed beds including pre-sowing seed treatment.

5 m2

b. Preparing potting mix and filling polypots, including all material for container seedlings. [Note 1 kg of 200 gauge polypots (4” x 7” laid

1000 nos.

0.04



0.04

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Seed

= 50 g

Bowl Trowel

10.00

flat) = 464 bags; 200 gauge black polythene is preferred.]

10.00

Polypot = 1050 nos. Sand m3

= 0.46

Soil m3

= 0.70

Compost = 0.23

135

Sieve Shovel


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) m3

c. Direct sowing of tree seeds into polypots including seed treatment, by sowing one seed in half the pots and two seeds in the other half.

1000 nos.

0.62

and

0.18

= 1500

0.18

Tray

nos. Wooden peg = 1 no. 1000 nos.

e. Pricking out tree seedlings and transplanting into beds.

Seed nos.

Wooden peg = 1 no.

100 d. Pricking out young seedlings transplanting into polypots.

0.62

0.12

0.12

Wooden peg = 1 no.

m2

136


Respec tive

No .



Description

Unit

Unskill ed Labour (person day) 0.12



Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

0.12

Khukuri Shovel

f. Transplanting grass slips into beds, from clumps. Slips are planted at 10 cm centres in rows 25 cm apart.

1000 nos.

0.60

g. Planting of hardwood cuttings of minimum 30 cm length to 20 cm depth into prepared beds. Cuttings spaced at 5 cm centres within rows, with 20 cm between rows.

0.60

Hessian jute = 0.30 m2

Hardwood cuttings = 1000 nos.

65.

18-4.5

Preparation of raised materials for extraction from the nursery

137

Khanti


Respec tive

No .



Description

Unit


a. Grass culm cutting production from nursery stock; single or double node (e.g. napier).

1000 nos.

b. Uprooting and preparing grass slips ready for site planting from nursery seedlings

1000 nos.



0.70

0.70

0.63

0.63

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)


Khukuri

Fork Hessian jute = 1.35 m2

Pickaxe Khukuri

c. Uprooting and preparing grass slips ready for site planting from nursery grass clumps raised from slips by vegetative propagation.

1000 nos.

0.33

0.33

Shovel Hessian jute = 4.20 m2

138

Khanti


Respec tive

No .


66.

18-4.6


Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Compost and mulch production

a. Mulch production by collection and cutting of weeds and other vegetation such as tite pati, banmara, etc. within 1 km of the road, and stacking along roadside.

1 m3

b. Compost production by collection and cutting of weeds and other vegetation such as tite pati, banmara, etc. within 1 km of the road, including fine cutting and filling compost pit.

1 m3

1.20

1.20

Doko

1 m3

0.10

0.10

Shovel

c. Turning compost once per month.

1.20

1.20

Hasiya Doko

139



S.

Respec tive

No .


Description

18-6

Direct seeding on site (same as S. No. 19)

67.

Unit


a. Broadcasting grass seeds on slopes < seeding rate 25 g/m2

400,

400,

b. Broadcasting grass seeds on slopes < including cover with long mulch, seeding rate 25 g/m2

100 m2

(persond ay)


0.17

0.17

5.00

5.00

100 m2

6.25 c. Broadcasting grass seeds on slopes < 400 450, including cover with long mulch and jute netting of mesh size 300 mm x 500 mm. Seeding rate 25 g/m2. Operation includes pegging with suitable live pegs or hardwood

Skilled Labour

100 m2

6.25

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Seed kg

= 2.50

Seed kg

= 2.50

Mulch = 5.00 m3

Seed kg

= 2.50

Mulch = 5.00

140

Khukuri Mallet (wooden hammer)


Respec tive

No .



Description

Unit




cuttings (e.g. simali) @ 1 m spacing, jute net of 6.75 m x 1 m size.

Equipment/ Tools

Royalties

Remarks

(personda y) m3

1.00 d. Sowing shrub or tree seeds on all slopes, at 25 cm intervals, including digging planting holes to 5 cm depth and covering with soil. Two seeds per planting hole.

Skilled Labour

Materials/

1.00

Jute net= 105 m2

Mild steel rod of 50 cm length

Live pegs = 128 nos.

100 m2

Seeds = 3200 nos. 68.

18-6

Planting grass cuttings on site

a. Planting single node culm cuttings of grass (e.g. napier) on fill slopes < 450 and

100

0.20

141

0.20

Grass cuttings = 100

Mild steel rod or hardwood


Respec tive

No .



Description

Unit


embankment slopes in plain areas. Approximate length 15 - 20 cm, including digging planting hole 10 - 20 cm depth using a metal rod or hardwood peg.

nos.

b. Planting single node culm cuttings of grass (e.g. napier) on hard cut slopes < 450. Approximate length 15 - 20 cm, including digging planting hole 10 - 20 cm depth using a metal rod or hardwood peg.

100

c. Planting single node culm cuttings of grass (e.g. napier) on hard cut slopes > 450. Approximate length 15 - 20 cm, including digging planting hole 10 - 20 cm depth using a metal rod or hardwood peg.



Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) nos. Hessian jute = 0.27 2 m

0.35

0.35

nos.

Grass cuttings = 100 nos.

100

0.50

nos.

0.50


Grass cuttings 142

peg of 50 cm length

Mild steel rod or hardwood peg of 50 cm length



Respec tive

No .



Description

Unit


d. Planting rooted grass slips on embankment slopes in plain areas, at 10 cm spacing within the row. The first row is 0.75 m from the edge of the pavement and subsequent rows are spaced at 1 m intervals down the embankment.

e. Planting rooted grass slips on slopes < 450 including preparation of slips on site. Operation includes digging planting holes to a maximum of 5 cm depth with metal rod or hardwood peg, depending on nature of soil. The planting drills should be spaced 10 cm apart.

1m

0.02



0.02

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

= 100


(personda y)

nos. Hessian jute = 0.27 2 m

1 m2

0.20

0.20

Grass slips = 11 nos. of drills Hessian jute = 0.14 m2 Line string

143

Mild steel rod or hardwood peg of 50 cm length Khukuri


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) =1m

Grass slips = 100 nos. of drills Hessian jute = 0.27 2 m

f. Planting rooted grass slips on slopes 450 600 including preparation of slips on site. Operation includes digging planting holes to a maximum of 5 cm depth with metal rod or

1 m2

0.30

144

0.30

Grass slips = 100 nos.

Mild steel rod or hardwood peg of 50 cm


Respec tive

No .



Description

Unit




hardwood peg, depending on nature of soil. The planting drills should be spaced 10 cm apart.

g. Planting rooted grass slips on slopes > 600 including

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) of drills

length Khukuri

Hessian jute = 0.27 2 m 1 m2

0.40

preparation of slips on site. Operation includes digging planting holes to a maximum of 5 cm depth with metal rod or hardwood peg, depending on nature of soil. The planting drills should be spaced 10 cm apart.


0.40

Grass slips = 100 nos. of drills Hessian jute 145

Khukuri


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) = 0.27 m2

69.

18-6

Planting shrub and tree seedlings and cuttings on site

a. Planting containerised tree and shrub seedlings, including pitting, transplanting, composting and placing tree guards, on toe of embankment slopes in plain areas, not less than 8 m from the road centre line. Pit size 30 cm diameter x 30 cm depth. Compost volume ¼ of the volume of the pit, mixed with original soil.

10 nos.

0.25

0.25

Container

Khanti

Seedlings = 10 nos.

Mallet (wooden hammer) Doko

Compost= 0.05 m3

0.33 146

0.33

Tree guard = 10 nos.

Khanti


Respec tive

No .



Description

Unit


b. Planting containerised tree and shrub seedlings, including pitting, transplanting, composting and mulching, on slopes < 300. Pit size 30 cm diameter x 30 cm depth. Mix compost with soil and backfill into pit, to ¼ of pit volume.

(personda y)

Skilled Labour

Equipment/ Tools

Royalties

Remarks

(personda y) Green mulch = 0.04 3 m

0.40

Seedlings = 10 nos. Compost= 0.05 m3

10 nos.

Doko

Khanti Doko

Green mulch = 0.04 3 m 0.17

d. Planting rooted tree stump cuttings and bare root seedlings, including pitting,

(persond ay)

Unskille d Labour

10 nos.

0.40 c. Planting containerised tree and shrub seedlings, including pitting, transplanting, composting and mulching, on slopes 300 450. Pit size 30 cm diameter x 30 cm depth. Mix compost with soil and backfill into pit, to ¼ of pit volume.

Skilled Labour

Materials/

10 147

0.17

Khanti


Respec tive

No .



Description

Unit


transplanting, composting and mulching, on slopes < 300. Pit size 10 cm diameter x 20 cm depth. Compost volume ¼ of the volume of the pit, mixed with original soil.

(persond ay)


Skilled Labour

Equipment/ Tools

Royalties

Remarks

(personda y) Seedlings = 10 nos.

nos.

0.25 e. Planting rooted tree stump cuttings and bare root seedlings, including pitting, transplanting, composting and mulching, on slopes 300 - 450. Pit size 10 cm diameter x 20 cm depth. Compost volume ¼ of the volume of the pit, mixed with original soil.

Skilled Labour

Materials/

0.25

Compost= 0.05 m3 Green mulch = 0.04 3 m

10 nos.

Seedlings = 10 nos. Compost= 0.03

148

Khanti


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) m3 Green mulch = 0.04 3 m

Seedlings = 10 nos. Compost= 0.03 m3 Green mulch = 0.04 3 m

149


Respec tive

No .



Description

Unit


f. Planting rooted tree stump cuttings and bare root seedlings, including pitting, transplanting, composting and mulching, on

10 nos.

0.33



0.33

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Seedlings = 10 nos. Compost= 0.03 m3

slopes > 450. Pit size 10 cm diameter x 20 cm depth. Compost volume ¼ of the volume of the pit, mixed with original soil.

70.

18-6.7

Green mulch = 0.04 3 m

Vegetative palisade construction, brush layering and fascines 1000

Adequate 150

Khanti


Respec tive

No .



Description

Unit


a. Collection of hardwood cuttings for planting material (e.g. assuro, namdi phul, simali) from sources within 1 km of road. Material to be approx. 1 m in length and minimum 5 cm in diameter.

nos.



0.85

0.85

0.17

0.17

0.12

0.12

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) supply of bushes.

Khukuri

1m b. Preparation and planting of live pegs of selected species (e.g. assuro, namdi phul, simali) of minimum 1 m length to 0.5 m depth into hard ground. Pegs spaced at 5 cm centres within rows, with 5 - 20 cm between rows, and interwoven with vegetation.

Live pegs = 20 nos.

Crow bar

1m

c. Preparation and planting of live cuttings of selected species (e.g. assuro, namdi phul, simali) of minimum 1 m length to 0.5 m into

Crow bar Live pegs = 20

151


Respec tive

No .



Description

Unit




soft debris. Pegs spaced at 5 cm centres within rows, with 5 - 20 cm between rows, and interwoven with vegetation.

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) nos.

1m 0.06

d. Site preparation for fascine laying: earth works in excavation of trench to 20 cm depth.

0.06

Pick axe Shovel

1m 0.17

e. Laying of live fascines, using live hardwood cuttings of selected species (e.g. assuro, namdi phul, simali) of minimum 1 m length, placed in bundles to give 4 running metres of cuttings per metre of fascine, including backfilling of trench and careful compaction.

0.17

Khukuri Shovel Hardwood cuttings of at least 1 m in length = 4 m

152


Respec tive

No .


71.

18-7


Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Jute netting works

a. For bare slopes and under planting with slips. Spinning raw jute from 100% jute fibre into yarn and weaving the yarn into netting. Hand spun yarn 5 to 8 mm in diameter, width of net 1.20 m, warp strands 27 nos. per 100 cm, weft strands 20 - 24 nos. per 100 cm, mesh size 30 - 40 mm square and 1.25 kg/m weight at 1.20 m widths. [Note. A tosro is the weaving shuttle, normally made from a split large bamboo culm.]

b. For holding mulch on slopes. Spinning raw jute from 100% jute fibre into yarn and weaving the yarn into netting. Hand spun

1 m2

0.36

0.36 Raw jute = 1.25 kg

Khukuri Bamboo sticks (10nos.) Weaving frame Tosro

1 m2

0.15

0.15 Raw jute = 0.26

153

Khukuri


Respec tive

No .



Description

Unit




yarn 3 to 5 mm diameter 1.20 m side and 11.2 m long. Mesh size 150 mm x 500 mm rectangular mesh and 0.25 kg/m at 1.20 m width. [Note. A tosro is the weaving shuttle, normally made form a split large bamboo culm.]

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) kg

Bamboo sticks (10nos.) Weaving frame Tosro

c. Placing 30 - 40 mm square mesh jute netting on bare slopes (for later underplanting with grass slips), including pegging with live hardwood cuttings or split bamboo pegs and loosening tension so that the net hugs the slope throughout.

1 m2

d. Placing 150 x 500 mm mesh jute netting to hold mulch on slopes, including application

1 m2

0.15

0.15

Woven jute net = 1.00 2 m Hardwood cuttings or spilt bamboo pegs = 5.00 nos.

0.10

0.10 Cut mulch

154

MS rod of 50 cm length Mallet (wooden hammer)

MS rod of 50


Respec tive

No .



Description

Unit




of mulch and pegging with live hardwood cuttings or split bamboo pegs and loosening tension so that the net hugs the slope throughout.

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) = 0.05 m3 Woven jute net = 1.00 2 m

cm length Mallet (wooden hammer)

Hardwood cuttings or spilt bamboo pegs = 5.00 nos.

72.

18-8

Fabrication cylinders

of

gabion

bolster Pick axe 1m

0.085

a. Site preparation for 30 cm diameter bolster: 155

0.085

GI wire = 2.00

Shovel


Respec tive

No .



Description

Unit




Skilled Labour

c. Manufacture of bolster panels: 70 x 100 mm hexagonal mesh wire construction (10 SWG frame and 12 SWG mesh).

Royalties

Remarks

kg 1m

0.360

0.360

Pick axe Shovel

1 m2

d. Construction of 30 cm bolster cylinder: placing, stretching wire mesh, filling with boulders, closing and backfilling.

1m

e. Construction of 60 cm bolster cylinder: placing, stretching wire mesh, filling with boulders, closing and backfilling.

1m

f. Construction of 30 cm bolster cylinder: placing, stretching wire mesh over 20 gauge black polythene sheeting, filling with

Equipment/ Tools

(personda y)

earth works in excavation of trench. b. Site preparation for 60 cm diameter bolster: earth works in excavation of trench.

Materials/

0.375

0.750

Boulders = 0.09 m3

0.375

0.100

0.750

0.100 Boulders = 0.36 m3

0.375

0.375

Gabion frame and tools

Gabion tools Doko

1m Gabion tools Black polythene = 0.40 156

Doko


Respec tive

No .



Description

Unit


boulders, closing and backfilling.

0.750

g. Construction of 60 cm bolster cylinder: placing, stretching wire mesh over 20 gauge black polythene sheeting, filling with boulders, closing and backfilling.

1m

h. Anchoring bolster: 12 mm diameter MS rebar cut into 2 m lengths for anchorage and placed at 1 m intervals.

1 no.

i. Laying of terram paper (geotextile).

1 m2


Unskille d Labour (personda y) 0.750

Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y) m2 Boulders = 0.09 m3

0.050

Doko

0.050 Black polythene = 0.80 2 m

0.050

Gabion tools

0.050

Gabion tools Doko

Boulders = 0.36 m3 Sledge hammer MS rod = 2.00 m

157

Khukuri


Respec tive

No .



Description

Unit




Skilled Labour

Materials/

Equipment/ Tools

Royalties

Remarks

(personda y)

Terram paper = 1.15 2 m 73.

18-9

Bamboo tree guards

a. Weaving bamboo tree guards using bamboo poles as uprights: 1.60 m in height; and weaving split bamboo with the outer wall intact around the posts. Dimensions of the guard are 0.60 m diameter x 1.30 m high.

1 no.

0.25

158

0.25

Bamboo = 2.20 nos.

Khukuri



WORK SPECIFICATIONS Specifications are required as 

governmental organisations need to standardise their works;



we need to be precise about the specifications in all aspects of engineering works;



we need to have sound information on which to base contracts.

Specification of the work specifies the nature and the class of the work, materials to be used in the work, workmanship, etc. and is very important for the execution of the work. The cost of a work depends much on the specifications. Specifications should be clear, and there should not be any ambiguity anywhere. From the study of specifications one can easily understand the nature of the work and what the work shall be. While writing specification attempts should be made to express all the requirements of the work clearly and in a concise form avoiding repetition. As far as possible, the clauses of the specification should be arranged in the same order in which the work will be carried out. The phrases ‘shall be’ or ‘should be’ are used while writing the specification. Specifications depend on the nature of the work, the purpose for which the work is required, strength of the materials, availability of the materials, etc. Types of Specifications: Specifications are of two types: 1. General specification or Brief Specification 2. Detailed Specification General specification or Brief Specification General specification gives the nature and class of the work and materials in general terms, to be used in various parts of the work. It is a short description of different parts of the work specifying materials, proportions, qualities, etc. General specifications give general idea of the whole work or structure and are useful for preparing the estimate. For example, 1:2:4 Plain cement concrete, Plastering with 1:4 Cement Sand mortar, Random Rubble Stone Masonry with 1: 6 Cement sand mortar, etc. are general specifications for some items of work.

159

CIVIL ENGINEERING BIOENGINEERING IV/I PREPARED BY: DKB Detailed Specification The detailed specification is a detailed description and expresses the requirements in detail. The detailed specification of an item of work specifies the qualities and quantities of materials, the proportion of mortar, workmanship, the method of preparation and execution and the methods of measurement. The detailed specifications of different items of work are prepared separately, and describe what the work should be ands how they should be executed and constructed. The detailed specifications are arranged as far as possible in the same sequence of order as the work is carried out. The detailed specifications if prepared properly are very helpful for the execution of the work.

SEASONAL PROGRAMMING OF BIOENGINEERING ACTIVITIES Activity

Througho ut year

Weeding Mulching Trimming Pruning Grass cutting Thinning Slope trimming Small slip clearance Repair of palisade Repair of fascines Repair to brush layering Repair of turfing Vegetation enrichment

160

In dry season

In winter

Complete before monsoon

CIVIL ENGINEERING IV/I Cleaning subsoil drain


Cleaning surface drain Repair of small engineering system Fire protection Protection of plants, planting sites Protection from grazing and theft of firewood and timber

References: 1. Roadsidebioengineernghandbook: Jhon Howell 2. Mountain Risk Engineering Handbook 3. Bio-engineering notes and field report

161

Bioengineering Note.doc

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