ABSTRACT The report is prepared after conduction a field visit under the department of civil engineering (Kathmandu Engineering College) according to the curriculum of Engineering Geology – I on Poush 23-24, 2072. In the field visit, we studied, observed, analyzed, and identified different types of rocks as per our theoretical course on the basis of geology and structures. The field visit was conducted in Malekhu, which has availability of different rocks natural topography in small extent of area and easy accessibility from the Kathmandu valley, a three hours bus travel along the Prithvi Highway from Kalimati. It gives us the clear ideas about the importance of geological structures in the field of civil engineering. This visit also provided us the knowledge regarding the different geological problems that are likely to occur during engineering works. The report includes all studies data, relevant photographs, theories, and discussion of geology of the site.
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ACKNOWLEDGEMENT At every step, an engineer has to encounter earth and earth, as a material or as construction site. So it proves the importance of geology to civil engineering professionals. He or she must go through the inner core of engineering geology for his/her perfection and for professionalism. The trip was really fruitful to us and certainly we got a lot of knowledge about the rocks and its structures. Thank you Dr. Kamal Kant sir and Dr. Subesh sir for sharing a part of his brain and to help us in field and giving complete suggestions. We also express our deep sense of gratitude to Ramin sir and Ganesh sir for guidance during field visit. Also thanks for the driver dai for taking us safely to the spot. At last, we would like to thank all our friends of other groups who cooperate kindly in team work ………………………... All of you did a wonderful job to lay out these pages. At last, we would like to express our gratitude to our college, Kathmandu Engineering College. We are proud to be students of Kathmandu engineering college Bibek Silwal (071bce031) Bikalpa Subedi(071bce032) Bikesh Karmacharya(071bce033) Bikram Dhungana(071bce034) Bipin G.C.(071bce035) 2071/BCE A2-R
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TABLE OF CONTENT 1.
Introduction……………………………………………………………… …. introduction of field work Objective of the study
Location of study area methodology limitations 02. Measurements of rock……………………
attitude
of
planar
features
of
Types of geological compass Instruments used during geographical study of malekhu
04. Geological traverse along malekhu Location L1 Location L2 Location L3 Location L4 Location L5 Location L6 Location L7 Location L8 Location L9 2071/BCE A2-R
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Location L10 Location L11 Photographs
05.Recognition of geological units Geological structures Phenomenon of geological structures Classification of geological structures Folds Observed Engineering significance of the geological structures Photographs 06.Conclusions……………………………………………………………… 07.References…………………………………………………………
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1.0 Introduction What lies on the earth and inside it? The curiosity gave birth the geology; the science of earth. It is an applied science, which deals with hills and mountains, valleys and Georges, and along lonely forests and rugged terrain. In geological fieldwork examination of the outcrops of rock, bodies upon the earth surface are carefully studied in details and reasonable inference on the geological structure and history of the region are drawn. With good approach to the geology and reasonable common sense of logical interpretation, one can form a neat picture of the geology of the region. The two days tour from we were taken to Malekhu for geological study. First day, we were taught to handle the geologist compass to measure dip and strike and we got ideas about river morphology, identification of 2071/BCE A2-R
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rock and different geological units of lesser Himalaya and Kathmandu nappy. However the two days trip was not sufficient to fulfill the thirst of us. 1.1 Introduction of field work This field work was done in the Malekhu area for the partial fulfilment of BE Civil Engineering degree under Tribhuwan University. The study team of students were accompanied and guided by our respected subject teachers during the field study in order to obtain knowledge about the geological structures, their engineering significance and distribution of different rocks and rock types.
1.2 Objectives of the Study To measure strike of bedding plane To measure the dip direction and dip amount of the bedding planes and joints To identify the rock type and its property. To be clear enough about joints, faults and folds.
1.3 Location of study area 2071/BCE A2-R
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Malekhu lies on lesser Himalayan unit of Nepal. It has peculiar geological features within a small range of area. The Malekhu V.D.C. of Dhading district lies about 70 Kms south west of Kathmandu valley and is located at latitude of 27o 50' 38'' to 27o 45' 50'' and longitude of 24o49'5'' to 84o50' 50’’. It is situated on the bank of Trishuli and Malekhu river. The Trishuli river is running from the eastern direction to the western diredtion and the Malekhu river from south to north which mingles into the Trishuli river. Also, the Malekhu river has a tributary namely the Apakhola which meets the Malekhu river at a distance about 3 kms from the Malekhu bazzar. Climatically Malekhu is a sub-tropical zone. Mainly the rainfall is during the monsoon.
1.4 Methodology The geological field study was carried out in the following ways: Field reconnaissance and geological traverse of the study site, Sketch of the field topography and rocks, Photographs of the field topography and rocks, Description of the field topography and rocks. The study team of students were accompanied and guided by our respected teachers during the field study. The rock samples were observed, the altitude 2071/BCE A2-R
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parameters of bedding planes were obtained by the use of Brunton Compass. The idea obtained was noted and photographs of important spots were taken. A film blow of hammer checks the strength and rock types (Igneous, Sedimentary and Metamorphic) were obtained and acid test were performed on the rocks
1.5 Limitations Malekhu was the best possible spot for this geological study while the time allocated was not enough for the detail study . The study could have been more effective if a little more time was provided. The field work was carried out and completed within two days, which means the study couldn’t be very thorough due to lack of time available, and the areas to be covered were more.
2. Measurement of Attitude of Planner Features Of Rock 2.1 Types of compass : 1. Clinometers compass: The compass, which can measure bearing and orientation with two sets. Since it doesn’t consist the sprit level, it should leveled by approximation and may not be accurate. 2. Burnton compass: It consists of sprit level and can measure bearing and inclination with relatively less error.
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3. Clar compass: It can read both inclination and bearing at once. Relatively easier to handle. 4. Digital compass: Displays digits as reading. Easy to handle. 5. Digital PC compass: The compass directly connected to the computer. Do not need to booking. 2.2 Instruments used during geographical study of / malekhu: 1.geological compass (Burnton compass) A geological compass is used to measure the attitudes of the geological features. The compass was mainly used for measuring the bearing of object with respect to north and to measure inclination .The main operation of geological compass consists of opening the compass carefully, leveling the spirit level and placing the compass on the planer feature for measurement. 2. Hammer A hammer was used to test the hardness of rock in the field. It was performed by striking the tip of the hammer and the surface of the rock whose hardness was to be determined and for the extraction of the sample. 3. IDENTIFICATION OF ROCKS Petrology is the scientific study of rocks. 3.1 Classification of rocks 1. Sedimentary rocks:
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The sedimentary rocks, as the name indicates, are those rocks which are derived from the consolidation of sediments of the preexisting rocks (igneous, sedimentary or metamorphic) under the influence of mechanical, chemical or organic activities of the denuding agents (i.e. wind, running water, glacier etc.) The products of wear and tear of the rocks due to natural agencies like blowing wind, running water, percolating underground water etc when subjected, under favorable conditions to sedimentation and subsequent compaction results in the formation of rock masses due to pressure and temperature conditions which are known as the sedimentary rocks. Well known examples are sandstone, lime stone, shale etc. 2. Metamorphic rocks: The rocks formed from the pre-existing rocks (igneous, sedimentary or metamorphic) by the processes of metamorphism (Greek, Meta=Change, morphe=form). It is a process by which existing rocks are modified under the influence of heat pressure or both The ultimate product of metamorphism of already existing igneous, sedimentary or even metamorphic rocks incorporating temperature, pressure, stress, chemically active substances are called metamorphic rocks, e.g. Slate, Marble, Schist, Gneiss, Phyllite.
3. Igneous rocks Primary or first formed rocks are called igneous (Latin, Ignis=Fire) rocks. It has been observed in deep wells, borings, mines, etc. that the temperature increases with the depth, generally there is an increase of 1o C for every 40m. depth. 2071/BCE A2-R
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The consolidation of magma results in the formation of igneous rocks e.g. of igneous rocks are granite, rhyolite. The magma remains in the molten state; so long its physical and chemical environments remain unchanged. But whenever some changes (pressure, temperature etc) takes place; the magma no longer remains in molten state, but is changed into solid state called rock. Those rocks, which are formed directly by the solidification of magma on the earth's surface or below it, are called igneous rock.
4. GEOLOGICAL TRAVERSE ALONG MALEKHU RIVER Location no. L1
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The first field spot of geology was conducted on the left bank of Malekhu River. It is located near broken bridge about 200m upstream from the Prithvi Highway.
S.N.
Physical Properties
1
Sample number 01
2
Color
Bluish grey
3
Texture
Crystalline
4
Grain size
Fine
5
Acid test
Vigorously reacts with HCl
6
Attitude
N 65° E/ 89° SE
7
Mineral comp.
Calcite
8
Scratch test
Scratched by hammer
9
Origin/rock type
Sedimentary
10
Identification
Dolomite (CaCo3.MgCo3)
11
Uses
Raw material for cement and sometimes in flooring
Location no.L2
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The next field visit was conducted on right bank of Malekhu River. It is located far from the Malekhu Bridge which is upstream about 400m from the Prithvi Highway. phyllite was found at this location. S.N.
Physical Properties
1
Sample number
02
2
Color
Silver white
3
Texture
Crystalline
4
Attitude
N 80° E/77° SE
5
Structures/cleavage Foliation plane/slaty
6
Grain size
Medium to coarse
7
Sp. Gravity
Low to medium
8
Acid test
No reaction
9
Origin/rock type
Low garde-Metamorphic
10
Engineering properties
Low strength
11
Identification
Phyllite
Location no.L3: 2071/BCE A2-R
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The outcrop was located at the left bank of Malekhu river about 300m upstream of previous location. Amphibolite was found at this location. S.N.
Physical Properties
1
Sample number
03
2
Color
Dark green
3
Texture
Crystalline
4
Attitude
N 23° W/ 85° SE
5
Structures/cleavage Foliation plane/slaty
6
Sp. Gravity
High
7
Mineral comp.
90% amphibole
8
Origin/rock type
Igneous (plutonic rock)
9
Engineering properties
High strength
10
Identification
Amphibolite
Magma intrusion into the robang phyllite. Hard, gave metallic sound when hammered. Massive rock, couldn’t found any exact orientation.
Location no.L4 2071/BCE A2-R
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The outcrop was located on the left bank of Malekhu river about 200m upstream of the river. S.N.
Physical Properties
1
Sample number
04
2
Color
Dirty white
3
Texture
Crystaline
4
Attitude
N 80° E/ 77° SE
4
Structures/cleavage Folliation plane/slaty
5
Grain size
Medium
7
Acid test
No reaction
8
Mineral comp.
Quartz
9
Origin/rock type
Low grade-Metamorphic
10
Engineering properties
High strength, durable
11
Identification
Quartzite
12
Uses
For making reeling in home applications,building stone, road metal, concrete aggregates
Location no.L5 2071/BCE A2-R
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The outcrop was located on the right bank of Malekhu river about 100m from the previous location upstream of the river. Schist was found in this location. S.N.
Physical Properties
1
Sample number
05
2
Color
Shiny green
3
Texture
Crystalline
4
Attitude
N 70° E/ 45° SE
5
Structures
Schistosity
6
Grain size
Medium
7
Sp. Gravity
Low to medium
8
Acid test
No reaction
9
Origin/rock type
High Grade-Metamorphic
10
Identification
Garnate Schist
Location no.L6 2071/BCE A2-R
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The outcrop was located on the left bank of Malekhu river about 200m from previous location. It was far from the broken bridge about 1100 upstream from the Malekhu river . Folds were studied on that area . Folds are the deformational structure on the rock strata formed due to compressional forces. Folds are created when high pressure is applied on rocks. When compressional force is applied , ptygmatic fold is found and when tensional force is applied boundinage is found. Typical fold had observed in this location and is described later.
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Location no.L7: The outcrop was located about 500-600m from the previous location upstream of the Malekhu river on the left bank of the river.
S.N.
Physical Properties
1
Sample number
07
2
Color
White
3
Texture
Crystalline
4
Structures
Foliation plane
5
Grain size
Coarse
6
Acid test
Vigorous
7
Mineral comp.
Calcite
8
Scratch test
Scratched by hammer
9
Origin/rock type
Metamorphic
10
Engineering properties
High strength, less porous, has rust due to iron of pyrite
11
Identification
Marble
12
Uses
As face works like flooring, wall panels, statue making, tabletops and other decorative works
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Location no.L8: The next field study was carried on the right side of the river near Malekhu-Dhading road on uphill side and on the appeal side of the road. S.N.
Physical Properties
1
Sample number
08
2
Color
White/light grey
3
Pattern
G I sheets
4
Attitude
: N 87° E / 36° NW
5
Grain size
Fine
6
Acid test
No reaction
7
Origin/rock type
Metamorphic
8
Identification
Quartzite rock
9
Description
It produces metallic sound. It is a primary rock.
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Location no.L9: The next field study was carried near Malekhu-Dhading road on the left side of the barhi khola. S.N.
Physical Properties
1
Sample number
09
2
Origin/rock type Metamorphic
3
Identification
Meta-sandstone
4
Structure
Cross Lamination
5
Description
Layer’s separated by color contrast
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Location no.L10 The next field study was carried along the Malekhu-Dhading road.
S.N.
Physical Properties
1
Sample number
10
2
Color
Black
3
Texture
Non crystalline
4
Attitude
N 153° E/ 32° SE
4
Structures
Foliation plane/slaty cleavage
5
Grain size
Fine
6
Sp. Gravity
Low to medium
7
Acid test
No reaction
9
Origin/rock type
Low-Grade metamorphic
10
Engineering properties
Low strength, slightly weathered, slaty cleavage and soapy feel
11
Identification
Slate
12
Uses
Roofing, in electrical industry as switch board, bases and various turned or shaped parts due to its insulating property
Location no.L11: 2071/BCE A2-R
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The outcrop was located about 500-600m from the previous location upstream of the Malekhu river on the left bank of the river. S.N .
Physical Properties
1
Sample number
11
2
Color
Light Grey
3
Texture
Crystalline
4
Attitude
N 80° E / 35° SE
6
Description
It had a metallic sound
8
Acid test
Vigorous
11
Origin/rock type Igneous Rock
12
Engineering properties
High strength
13
Identification
Granite
13
Uses
As aggregates, foundations in the construction and as slab
Thus all three types of rock we had found at our field area. Mostly there were metamorphic rock and then sedimentary and lastly igneous. For civil engineers, only identification of rock is not sufficient. He or she should have an idea about the engineering significance of specific rock type. We all had learnt on this basis and partially we got it too. 2071/BCE A2-R
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PHOTOGRAPHS
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5.0 RECOGNITION OF GEOLOGICAL UNITS: Nepal lies at active tectonic region. Indian plate has been penetrating the Asian plate continuously. Due to this several thrusts were formed and forming till today .the Himalayas also formed due to tectonic activity.
5.1 Geological structures Geological structure is the study of the permanent deformation and rock failure created by the changes in stress through geologic time. It is by far the most important aspect of geology for the engineer to understand. Tectonic processes are responsible for the many discontinuity planes (fractures, faults, joints) that permeate rock masses controlling their strength, stressstrain characteristics and the transmission and storage of fluids. The stress due to various geological processes such as tectonic activities, earthquake, volcanic activities, etc tends to displace and distort the rocks within the earth. 5.2 Phenomenon of geological structures Phenomenon of structures subdivided into two groups:
may
be
conveniently
Brittle structures - recording the brittle-elastic failure of rocks in the past. Faults and joints fall in this broad category. Ductile structures - preserving the permanent viscoplastic deformation of rock throughout geologic time. Folds and metamorphic foliations are the expression of this type of structure. 2071/BCE A2-R
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5.3 Classification of Geological Structure 5.3.1 Primary Structures Primary Structures are those which are formed at the time of rock formation. It often allows us to determine the original facing direction of strata and are also useful in age determination. Some major primary structures are as follows : a) Bedding b) Mudcrack c) Ripple Mark d) Cross Lamination a. Bedding Beds refer to the layers of sedimentary rock that posses almost planar top and bottom surfaces. These layers are often easily distinguished on the basis of variation in color, composition and grain size. Beddings are planar top and bottom surface of the beds. These are the planes of weakness. Beds are classified according to their thickness such as very thick bedded (above 100cm) , thick bedded (30com – 100cm),medium bedded (10cm30cm) and thin bedded (1cm-10cm). b. Mudcrack Mudcrack are sedimentary structures which are formed as sediment dries and contracts .These primary 2071/BCE A2-R
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structure are concave in shape . They are concave toward original direction of bed. c. Ripple Mark These are the sedimentary structures in which the sediments are deposited in the form of wave by the action of flowing water . The shallow slope faces of source of flow create ripple marks. There are two types of ripple marks : a) Oscillation Ripple Marks b) Current Ripple Marks d. Cross Lamination Deposition of sediments in different sets that make an angle with each other is known as cross lamination . Truncation occurs on upper portion of bed. Younging direction is on concave side of cross lamination. 5.3.2 Secondary Structures Secondary structures are those which are formed after the time of rock formation. Secondary structures mainly consists of metamorphic rocks . Some of the secondary structures are as follows : a) Fold b) Fault c) Thrust a. Folds: Folds are ductile deformation on the structure. They are the strata permanently deformed either by buckling or fracturing, if subjected to stress in a rock 2071/BCE A2-R
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mass, and they cannot resist. Type of deformation depends upon mechanical properties of rocks and the nature of stress when applied slowly deep on the earth. Folds are the ductile deformation which does not rupture or fracture the rock but instead caused them to permanently bend. Ductile deformation most often occurs well below the earth’s surface. The classifications of folds are:a) Based on upward and downward bend: • Anticline fold • Syncline fold b) Based on the basis of relationship of axial plane to limbs: • Symmetrical fold • Assymetrical fold • Recumbent fold • Overturned fold c) Based on the hinge line • Non-Plunging fold • Plunging fold d) Based on the behavior of depth • Similar fold • Parallel fold e) Based on the shape • Rounded fold 2071/BCE A2-R
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• Angular fold • Chevron fold • Box fold f) Based on the mode of occurrence • Synclinorium • Anticlinorium b. Fault Fault is a rupture plane along which the opposite walls are moved each other. This movement may vary from a few cm to many km depending upon the magnitude and nature of the stress and the resistance offered by the rocks. The faults are also caused due to earthquake but it is still a complicated geological problem, which awaits satisfactory solution. Whether the earthquakes are caused due to faulting or faults are caused due to earthquake. The fault is occurred due to the plate movements, which creates the shear stress. The metamorphic form of gauge and breccia is called mylonite.
The classifications of faults are as: a) Geometrical classification: • Strike fault • Dip fault • Oblique fault b) Genetic classification 2071/BCE A2-R
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• Normal fault • Reverse fault • Strike slip fault c. Thrust A kind of reversed fault in which the hanging wall has actually moved relative to the footwall is called thrust. It is also known as low angle reverse fault. There are mainly following thrusts. 1) Main central thrust 2) Main boundary thrust 3) Main frontal thrust The Mahabharat range lies between MFTand MBT. Similarly, siwalik range lies below MFT. Our Study area lies between Kathmandu complex and nuwakot complex, both is the member of Mahabharat synclonyrium. The study area starts from Maleuku dolomite, robang formation (robang phyllite with rock quartzite) to raduwa formation ( garnetiferous schist). This is the boundary between nuwakot and Kathmandu complex and known as Mahabharat thrust.
5.4 Folds Observed Ptygmatic Fold The folds are created when high pressure is applied on rocks. The pressure is applied due to compression ptygmatic fold is formed 2071/BCE A2-R
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Boundinage Fold The fold created due to tensile pressure boundinage fold is formed. 5.6 Engineering significance of the geological structures The most striking features of rocks as engineering materials is that they are not simple, isotropic, elastic and continuous but very complex, strongly anisotropic, inelastic discontinuous. It is virtually impossible to deduce the stress history of rocks from their observed deformation. There are always many ambiguous deformation paths that could have been followed to produce what is observed.
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7.0 CONCLUSIONS: At last we had concluded the malekhu and its surrounding is the answer for geological curiosity. Actually, the malekhu is small in area but it has large amount or numbers of the geological phenomenon and hence it can provide broad knowledge for the learners Minimum knowledge require for engineers in geology field is fulfilled in this trip. Along the Malekhu River, we found sedimentary rock and gradually metamorphosed from phyllite to crystalline schist and along the way to Dhading, it gradually metamorphosed to lime stone to phyllite and then to slate. Every major bed was dipped in north direction. This proved the tectonic movement along the way from south to north. Handling the compass and to measure the attitude of rock outcrop is now very easy to us. Finally it will be better to say that if there had not been any geological trip,we would not have learnt a lot of these information as theoretical knowledge is not enough for field work. So this geological field work helped a lot us for study and later on during field works. .Really ...........beyond expectation! We do salute to our respective teachers again!!
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REFERENCES: Data collected during the field visit Sketches drawn and photo taken in the field www.wikipedia.com http://www.geology.edu.np Engineering Geology: By Prakash Chandra Ghimire Mahesh Singh Dhar A Text Book of Engineering Geology Recent Publications related to the subject matters and other sites.
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