1
2
Highway Alignment and Surveys Highway alignment:The position or the layout of the centre line of the highway on the ground is called the alignment. The horizontal alignment. The horizontal alignment includes the straight path, the horizontal deviations and curves, changes in gradient and vertical curves are covered under vertical alignment of roads. A new road should be aligned very carefully as Improper alignment would result in or more of the following disadvantages:a)
Increase in construction cost.
b)
Increase in maintenance cost.
c)
Increase in vehicle operation cost.
d)
Increase in accident rate. Once the road is aligned and constructed, it is not easy to
change the alignment due to Increase in cost of adjoining land and construction of
costly structures by the road side. Hence the
important of careful consideration while finalizing the alignment of a new road need not be over emphasized. Requirements:The basic requirements of an ideal alignment between 2 terminal stations are that it should be : a) short. b) Easy c) Safe d) Economical.
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Short: -It is desirable to have a short alignment between two terminal stations.
A Straight
alignment
would
be
though there may be several practical considerations would cause deviation from the
shortest which
shortest path.
Easy: - The alignment should be such that its is easy to construct and maintain
the roads
alignment should be
with
minimum
problems.
Also
the
easy for operation of vehicles with easy
gradients and curves. Safe: - The alignment should be safe enough for construction and maintenance from the view point of stability of natural hill slopes,
embankment and cut slopes and
embankments also it
foundation
of
should be safe for the traffic operation with
geometric features. Economical:- The road alignment could be considered economical only if the total cost including initial cos5, maintenance cost and vehicle operation cost is lowest. All these factors should be given due consideration before working out the economics of each alignment. The alignment should be such that it would offer maximum utility by serving maximum population and products. Factors controlling alignment For alignment to be shortest, it should be straight between the 2 terminal stations. This is not always possible due to various practical difficulties such as intermediate obstructions and topography. A shortest route may have very steep gradients and hence not easy for vehicle operation. Similarly, there may be construction and maintenance problems along a route, which may otherwise be short and easy. Roads are often deviated from the shortest route in order to cater for intermediate places of importance or obligatory points. A road which is economical in the initial construction cost, need not necessarily be the most economical in maintenance or in vehicle operation cost. It may also happen that the shortest and 4
easiest route for vehicle operation may work out to be the costliest of the different alternatives from construction viewpoint. Thus it may be seen that an alignment can seldom fulfil all requirements simultaneously; hence a judicial choice is made considering all factors. The various factors that control the highway alignment in general may be listed as: a) b) c) d) e)
Obligatory points. Traffic Geometric design Economics Other considerations.
In hill roads additional care has to be given for; a) Stability b) Drainage c) Geometric standards of hill roads and d) Resisting length a) Obligatory Points: There are control points governing the alignment of the highways. These control points may be divided broadly into 2 categories. 1) 2)
Points through which the alignment is to pass Points through which the alignment should not pass.
1)
Obligatory points through which the road alignment has to pass may cause the alignment to often deviate from the shortest or easiest path.
2)
Obligatory points through which road should not pass also may make it necessary to deviate from the proposed shortest alignment. The obligatory points shortest alignment. The obligatory points which should be avoided while aligning a road include religious places, very costly structures, unsuitable land etc.,
b) Traffic: The alignment should suit traffic requirements. Origin and destination study should be carried out in the area and the desire lines be drawn showing the trend of traffic flow. The new road to be aligned should keep in view the desired lines, traffic flow patterns and future trends.
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c) Geometric design: Geometric design factors such as gradient, radius of curve and sight distance also would govern the final alignment of highway
Engineering surveys for highway locations. Before a highway alignment is finalised in highways project, the engineering surveys are to be carried out. The surveys may be completed in 4 stages. The stages of the engineering surveys are: 1. 2. 3. 4.
Map study. Reconnaissance. Preliminary surveys Final location and detailed surveys.
1. Map study: If the topography map of the area is available, it is possible to suggest the likely routes to the road. In India, topographic maps are available from the ‘Survey of India’ with 15 or 30m countdown intervals. The main features like rivers, hill, valleys, etc., are also so shown on these maps. By careful study of maps, it is possible to have an idea of several possible alternate routes so that further details of these may be studied later at the site. 2. Reconnaissance: The second stage of surveys for highway location is the reconnaissance to examine the general character of the area for deciding the most general character of the area for deciding the most feasible routes for detailed studies. A field survey party may inspect a fairly road stretch of land along the proposed alternative routes of map in the field. Only very simple instrument like abney level, tangent clinometer, barometer etc., All relevant details not available in the maps are collected and noted down. Valleys, ponds, lakes, marshy land, ridge, hills, permanent structures and other obstructions along the route which are not available in the map. Approximate values of gradient, length of gradients and radius of curves of alternate alignments.
Preliminary survey: 6
The main objectives of the preliminary survey are. 1. To survey the various alternate alignments proposed after the reconnaissance and to collect all the necessary physical information and details of topography, drainage and soil. 2. To compare the different proposals in view of requirements of a good alignments. 3. To estimate quantity of earthwork materials and other construction aspects and to workout the cost of alternate proposals. 4. To finalise the best alignment from all considerations. Final location and detailed survey: The alignment finalised at the design office after the preliminary survey is to be first located on the field by establishing the centre line. Next detailed survey should be carried out for collecting the information necessary for the preparation of plans and constructions details for the highway project. Location: The centre line of the road finalised in the drawings is to be translated on the ground during the location survey. This is done using a transit theodolite and by staking of the centre line. The location of the centre line should follow, as closely as practicable, the alignment is finalised after the preliminary surveys. Detailed surveys: Temporary benchmarks are fixed t interval of about 250 metres and at ll drainage and under pass structures. Levels along the final centre line should be taken at all staked points. Levelling work is of great importance as the vertical alignment, earth work calculations and drainage details are to be worked out from the level notes. All river crossing, valley etc., should be surveyed in details upto considerable distances on either side. CBR values of soils along the alignments may be determined for designing the pavement.
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Drawing And Report Drawings: 1. Key plan showing the road between maklidurga railway stations and hadonahally, via temple. 2. Contour plan of the given real stretch of length 1.0 km and given width, showing all details of the road and other features (Plane table and direct conforming). 3. Longitudinal section showing all details including the centre line of existing road and realigned road after redesign. Scale: 1cm=20m (PLAN) 1=2000 horizontal, 1=200 vertical. 4. Total 10 typical c/s are taken at straight and curved sections of the road showing existing cross section details(Including shoulder and side drains and proposed sections after realignment, scale and of the proposed sections after realignment) Scale: 1=100(Vertical) 1=100(Horizontal) 5. Typical pavement cross sections: All the drawing should be done by individual batches on the same day of the work and should be shown to the concerned staff. Estimates: The project estimates should consist of general abstract of cost and detailed estimates for each major head. Project Report: The project report forms an important part of the project document. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Objectives. Minimum geometric design standards as per IRC. Field work details. Geometric deficiency and re-design details. Laboratory work and graphs. Pavement design details. Mix design details. Estimation of quantities of materials Drawing Recommendations. 8
Highway Project: New Highway Project: The new highway project work may be divided into the following stages; 1. 2. 3.
Route selection. Collection of materials. Construction stages including quality control
Steps in new project work: 1. Map study
: With help of available topographic maps of the area.
2. Reconnaissance Survey: A general idea of a topography and other features, soil identification. 2
3. Preliminary survey survey
: Topographic details and soil along alternate alignments, consideration of geometric design
and other requirements of alignments. 4. Location of final alignments driving pegs chosen 5. Detailed survey
: Transfer of the alignment from the drawings to the ground by along the centre line of finally alignment. : Survey of the highway construction work for preparation of longitudinal
and cross-sections, computations of earth work, quantities and other construction materials and details of geometric design. 6. Materials survey their
: Survey of construction materials, collection and testing.
7. Design cut
: Design details of embankment and
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slopes, foundation of embankments and bridges, pavement layers. 8. Earth Work
: Excavations for highway cutting and drainage system, construction of embankments.
9.Pavement Constructions : construction
Preparation
of
sub-grade
of sub-base and surface courses. 10. Construction Controls
: Quality control tests during different stages of constructions and to check the road.
Re-alignment project Necessity of re-alignment: 1. Improvements of horizontal alignment design elements, such as radius, super elevation, transition curves, clearance on the inner side of the curve of shifting the curve to provide adequate sight distance elimination of reverse curves and undesirable zig-zag etc., 2. Improvements of vertical alignments like steep gradients, changes in summit curves to increase sight distance. Correction of undesirable undulations like humps and dip etc., 3. Raising the level of a portion of a road which is subjected to flooding, submergence or water logging during monsoons. 4. Re-construction of weak and narrow bridges, and culverts and changes in water-way at locations slightly away from the existing site. 5. Construction of over bridges or under bridges 6. Construction of a bypass. 7. Defence requirements.
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Highway Geometric Design Importance of geometric design: The geometric design of a highway deals with the dimensions and layout of visible features of the highway such as alignment, sight distances and intersections. The geometrics of highway should be designed to provide optimum efficiency in traffic operations with maximum safety at reasonable cost. The designer may be exposed to either planning of new highway new work or improvement of existing highways to meet the requirement of the existing and anticipated traffic. It is possible to design and construct the pavement of the road in stages; but it is very expensive and rather difficult to improve the geometric elements of a road in stages at a later date. Geometric design of highway deals with following elements: 1. 2. 3. 4. 5.
Cross section elements Sight distance considerations Horizontal alignment details Vertical alignment details Intersection elements
Highway Cross-Section Elements: Pavement surface characteristics: The pavement surface depends on the pavement type which is decided based on the availability of materials and funds, volume and composition of traffic, sub-grade and climatic conditions, construction facilities and cost consideration. Friction: The friction between vehicle tyre and pavement surface is one of the factors determining the operating speed and distance requirements in stopping and accelerating the vehicles. When a vehicle negotiates a horizontal curve, lateral friction developed 12
counteracts the centrifugal force and thus governs the sage operating speed. Skid occurs when slide without revolving or when the wheels partially revolve. When the path travelled along the road surface is more than the circumferential movements of wheels due to their rotation. Slip occurs when a wheel revolves more than the corresponding longitudinal movement along the roads. Longitudinal friction coefficient values of 0.35 to 0.40 have been recommended by IRC depending on speed. For horizontal curve design, IRC has recommended the lateral coefficient of friction of 0.15. Pavement uneveness: Pavement uneveness measured using Profilograph, Profilometer or Roughometer. An equipment capable of integrating the uneveness of pavement surface to a cumulative scale and that gives the uneveness index of the surface in cm/km length of road. The U.S. Bureau of public roads Roughometer is one such device which could be towed by an automobile. Uneveness Index Cm/km In old pavements In Below 95 95 to 119 120 to 144 145 to 240 Above 240 In new Pavements Below 120 120 to 145 Above 145
Riding Quality Excellent Good Fair Poor (Possible resurfing) Very Poor (resurfing required) Good (acceptable) Fair (acceptable) Poor (not acceptable)
Cross Slope or Camber: Cross slope or Camber is the slope provided to the road surface in the traverse direction to drain off the rain water from the road surface. Important reason: 1. To prevent the entry of surface water to the sub grade soil through pavement, the stability, surface condition and life of the pavement get adversely affected if the water enters in the sub-grade and soil gets soaked. 13
2. To prevent the entry of water into the bituminous pavement layer. Types of road surface
Range of Camber
Heavy to Light Cement Concrete and high 1 in 50(2.0%) type bituminous surface 60(1.7%) Thin bituminous surface 1 in 40(2.5%) 50(2.0%) Water bound macadam 1 in 33(3.0%) 40(2.5%) Earth 1 in 25(4.0%) 33(3.0%)
1. 2. 3. 4.
to
1
in
to
1
in
to
1
in
to
1
in
For the project: Thin bituminous surface of 1 in 40 Camber is selected. Width of pavement or Carriageway: The pavement or carriageway width depends on the width of traffic lane and number of lanes. The lane width is determined on the basis of width of vehicle and minimum clearance, which may be provided for safety. 1. 2. 3. 4. 5.
Class of road Single lane Two lanes, without raised kerbs Two Lanes with, raised kerbs Intermediate Carriageway Multi-lane pavements
Width of Carriage way 3.75m 7.0m 7.5m 5.5m 3.5m per lane
For the project: Two lanes with raised kerbs of 7.5m carriageway is selected. Kerbs: Kerbs indicates the boundary between the pavements and shoulder; or some times islands or foot path or kerb parking space. 1. Low or mountable type kerbs which remain in through traffic lanes, yet allow the driver to enter the shoulder area.
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2. Semi-barrier type kerb is provided on the periphery of roadway where the pedestrian traffic is high. Kerb is 15cm above pavement. 3. Barrier type kerb is provided in built up areas adjacent to foot paths with considerable pedestrians traffic. Height of kerbs is above 20cm from pavement. In rural roads submerged kerbs are sometimes provided at pavement edge between edge and shoulders. Road margins: The various elements included in road margins are shoulder, parking lane, frontage roads, driveway, cycle track, footpath, guard rail and embankment slope. Shoulders are provided along the road edge to serve as an emergency lane for the vehicle compelled to be taken out of pavement or raodway. The minimum shoulder width recommended by IRC is 2.5m Footpaths or side walks are provided in urban areas when the vehicular as well as pedestrian traffic are heavy. Embankment slopes should be as flat as possible for the purpose of safe traffic movement and also aesthetic reasons. Width of Roadway or formation: Width of Roadway is the sum of widths of pavements or carriageway. Including separators if any; and the shoulders. The width of Roadway as per IRC Sl No 1. 2. 3.
Roadway width, m Plain Rolling Mountains and terrain steep terrain
Road Classification National and State Highway a) Single lane b) Two lane Major district roads a) Single lane b) Two lane Other district roads a) Single b) Two lanes 15
12.0 12.0
6.25 8.80
9.0 9.0
4.75 -----
7.5 9.0
4.75 -----
4.
Village roads-single lane 7.5 Major district road 9.0m may be taken
4.00
Right of Way: Right of way is the area of land acquired for the road, along its alignment. The land width is governed by following factors: 1. Width of formation depending on the category of highway and width of roadway and road margins 2. Height of embankment, side slopes, drainage system, sight distances. Recommended land width of different roads:
Sl. No
Road Classificatio n
Plain and rolling terrain Open areas Normal
1. 2. 3. 4.
Built areas
Range
Normal
Range
National and 30state 45 30 30-60 60 highways Major district 2525 20 15-25 roads 30 Other District 15 15-5 15 15-20 roads Village 1212 10 12-15 Roads 18 For major district road 25-30m land width may be
Mountains and steep terrain Open Built areas areas Normal
Normal
24
20
18
15
15
12
9
9
acquired.
Sight distances: Safe and efficient operation of vehicle on roads depends, among other factor on road length at which an obstruction, of any, becomes visible to the driver in the direction of travel. Sight distance available from point is the actual distance along the road surface. Stopping sight distance: 16
The sight distance available on a highway at any spot should be of sufficient length to stop a vehicle travelling at design speed. Design, speed, kmph SSD in m
20
25
30
40
50
60
65
80
100
20
25
30
45
60
80
90
120
180
SSD for given 65 kmph=93m. Hence designed SSD is as per IRC.
Over taking sight Distance(OSD) If all vehicles travel on a road at the design speed, then theoretically there should be no need for any over taking. In fact vehicles do not move at the designed speed and particularly under mixed traffic conditions. The minimum distance open to vision of the driver of a vehicle intending to overtake slow vehicle ahead with safety against the traffic of opposite direction is known as the minimum overtaking sight distances(OSD). IRC recommended OSD values: Speed kmph 40 50 60 65 80 100
Time component, seconds For For overtaking opposing Total manocurve vehicle 9.0 6.0 15 10.0 7.0 17 10.8 7.2 18 11.5 7.5 19 12.5 8.5 21 14.0 9.0 23
Safe overtaking sight distance (metres) 65 235 300 340 470 640
As per IRC recommendation and designed data results are same. OSD for 2-way traffic is assumed to be = 340m Overtaking Zones: It is desirable to construct highways in such a way that the length of road visible ahead at every point is sufficient for safe overtaking. Overtaking opportunity for vehicles moving at design speed should be given at frequent intervals. These zones which are meant for overtaking are called overtaking zones. Design of horizontal alignment: 17
Design speed: The design speed in the main factor on which geometrics design elements depend. The sight distances, radius of horizontal curve, super elevation, extra widening of pavement length of summit and valley curves are all dependent on design speed.
Horizontal Curves: A horizontal highway curve is a curve is a plan to provide change in direction to the central line of a road. When a vehicle traverses a horizontal curve, the centrifugal force acts horizontally outwards through the centre of gravity of the vehicle. P=WV2 gR P=Centrifugal force W=Weight of vehicle,Kg R=Radius of circular curve,m V=Speed of vehicle, m/sec G=acceleration due to gravity=9.8m/sec Centrifugal force acting on a vehicle negotiating a horizontal curve has 2 effects: 1. Tendency to overturn the vehicle outwards about the outer wheels and 2. Tendency to skid the vehicle laterally, outwards. Super elevation: In order to counteract the effect of centrifugal force and to reduce tendency of vehicle to overturn or skid. Outer edge of pavement is raised with respect to inner edge. If the speed of vehicle is represented as V Kmph e +f= V2 127R
Stopping sight distance: 1. Calculate SSD on highway for design speed of 65kmph?
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Assume total reaction time ‘t’ may be taken as 2.5 seconds and design co-efficient of friction as f= 0.35 V=65kmph g=9.81m/sec2 V=65 = 18.05m/sec 3.6 SSD=Vt+V2 2gf =18.05x2.5+ 18.052 2x9.81x0.35 =45.125+47.47 SSD=92.59m As per IRC 65 kmph OSD is 90 kmph
Over taking sight distance 2) Design O.S.D for designed speed of 65 kmph? Solution:O.S.D = (d1 + d2 + d3) V= 65Kmph A= 3.28kmph/sec from table Assume Vb = V-16 = 65 – 16 = 49 kmph Assume reaction times as 2.5 seconds. d1 = 0.28 Vb x t = 0.28x49.2.5 = 34.3m d2 = 0.28 Vb x t + 25 = (0.28x49x8.32) + (2x15.8) = 145.75m S = (0.2 Vb + 6) = 0.2x46+6 = 15.8m 14.4 xS T=
A
14.4 x15.8 =
3.28
= 8.32 sec
d3 = 0.28 VT = 0.28 x65x8.32=151.42m OSD fpr 2-way traffic = d1 + d2 + d3 OSD = 34.3+145.75+151.42 19
OSD = 331.47m AS per IRC 65kmph OSD is 340m
1.
WET SIEVE ANALYSIS
2.
CONSISTENCY LIMITS
3.
CAMPACTION TEST
4.
CALIFORNIA BEARING RATION TEST
5.
FIELD DENSITY BY SAN REPLACEMENT METHOD
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Grain size analysis Aim: -To determine the soil distribution is by sieving Apparatus: balance, rubber shaker. Procedure:-
Set of standard sieves of different sieve sizes, covered pestle and mortar, oven riffle, sieve
1) Wet sieving may be adopted in the case of clayey or cohesion soil or when the soil is not grained. 2)
The soil finer than 2mm size is oven dried at 105 o to 110oc and required quantity taken by riffling is weighed. This sample is spread in a tray or bucket and covered with water.
3) In case of soils having fractions that are likely to flocculate a dispersing agent like sodium hexametaphosphate (2.0g) of sodium hydroxide (1.0) and sodium carbonate per liter of water may be added to the water. The mix is stirred and left for soaking. 4) The soaked soil specimen is placed over set of sieves of sizes with the finest sieve and pan at the bottom and washed thoroughly. 5) Washing is continued till the water passing each sieve is substantially clean. The fraction emptied carefully dried and weighed separately. Tabular Column :-
Sl No 1 2 3
Sieve Openin g Particle size(m m) 4.75 2.36 1.18
Mass of soil retaine d
%retianed = mass of soil mass of soil
Cummalati ve % retained
% finer
5.2 9.8 19.7
1.04 1.96 3.94
1.04 3.0 6.94
98.96 97.00 93.06
21
4 5 6 7 8
600 300 150 75 pan
29.7 82.7 112.2 64.9 175.8
5.94 16.54 22.44 12.98 35.16
12.88 29.88 51.86 64.84 100
87.12 70.58 48.14 35.16 0
Result:- The given soil contains 1) Gravel =1.04% 2) SAND=61.84% 3) Silt and clay = 35.16%
Consistency limits determination using casagrande type mechanical liquid limit apparatus. Materials and equipments:1) 2) 3) 4) 5) 6) 7) 8) 9)
liquid limit apparatus consisting of a brass cup and rubber. Grooving tools with 1cm gauge handle. ASTM and casagrande (BS) type. Glass plate about 40cm square 425 micron sieve electronic weighing machine moisture containers oven of oven 105o - 110oc stop watch
Procedure : 1) By means of the grooving tool gauge and adjustment plate, adjust cup of the liquid limit apparatus to fall exactly 1cm on the point of contact on the base. 2) Take about 150gm of an air dried soil samples passing 425micron. Sieve and mix thoroughly with distilled water to give a stiff and uniform paste/ leave the soil for a suitable maturing time which may extend upto 24 hrs for heavy clays. 3) Place a portion of the paste in the cup, level off with a spatula the top surface symmetrically to give a maximum depth of 1 cm cut a uniform, straight groove by drawing firmly a grooving tool through the soil paste along the diameter through the centre of the hinge.
22
4) Turn the handle at a rate of 2 revolutions per second and count number of blows until the 2 pars of soil come in contact at the bottom of the groove along a distance of about 13-mm. The groove should be closed by a flow of the soil and not by slippage. 5) Record the number of blows at which the groove closes. Remove about 15g of soil forming the edges of the groove that flowed together and determine the water content by oven-drying. 6) Transfer the remaining soil in the cup to the main soil sample on the glass plate and mix thoroughly after adding a small amount of water, clean the cup and grooving tool. 7) The test should always proceed from the drier to the wetter condition of the soil. Least of 4 tests readings were given ranging from 15 to 40 blows for each addition of water soil is mixed for at least 5 minutes.
Observation: Test No No. of flows Container No Mass con + wet soul(gm) Mass of cont + dry soil(gm) Mass of empty container moisture content(% ) Liquid limit(grap h)
1
2
3
10
21
23
05
07
1
16.4
12.6
15.2
14.9
11.9
14.4
9.1
8.6
10.1
25.86
21.21
18.6
17.5%
Result:- The given soil has liquid limit = 17.5%
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Plastic limit test Object:-
To determine the plastic limit of a soil and also to calculate the plasticity index.
Apparatus:Porcelain dish, about 12-cm in diameter spatula, about 2-cm wide ground –glass plate about 20cm by 15cm, oven, rod, 425micron sieve electronic weighing machine. Procedure: 1) Mix thoroughly about 30g of soil passing a 425 micron sieve with distilled water in the evaporating dish or on the glass plate until it is plastic enough to be shaped into a small ball. 2) Take about 10gm of the plastic soil mass. Form a ball of it and them roll into a thread with the fingers on the ground – glass plate. When a diameter of 3-mm is reached, remoulded the soil again into a ball. 3) Repeat this rolling and remoulding process until the thread starts just crumbling at a diameter of 3mm. Keep the crumbled threads for moisture content determination. 4) Repeat the test twice more with fresh samples and calculate the plastic limit Wp as the average of three moisture contents. Plasticity Index:-zero After determining the liquid limit Wl and plastic limit Wp, plasticity index is calculated as Ip = Wl - Wp Result:- The soil is silt and non-plastic soil as plastic limit is zero. HRB Classification:-A-4
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Compaction Test Object:- To determine the optimum moisture content and maximum dry density. Apparatus:- Cylindrical mould, rammer, mould accessories, IS sieves. Procedure:1) Take a representive sample weighing approximately 20kg of thoroughly mixed dried material passing 4.75mm Is sieve. 2) Clean the mould and fix it to the base take the empty weight of the mould . the inside of mould is greased. 3) At least attach the collar to the inside of the mould is greased. 4) Mix the soil thoroughly take about 2.5kg of soil and compact it, in the mould in 3 layers and each layer he being compacted by 25 blows. 5) Remove the collar and cut the excess soil with the help of straight edge clean the mould from outside and weigh it to nearest gram. 6) Repeat step 4 and 5 for about 5 or 6 time using a fresh part of soil specimen and after adding a higher water content than the proceeding specimen.
Observation Diameter of mould = 10cm = d Height of mould = 12.6cm = h Volume of mould = 989.6cm = v Type of test = Heavy compaction. Weight of rammer = 4.89kg No. of layers = 3 No. of blows/layer =56 25
Tabular column Determinati on on Mass mould + comp soil (gm) Mass comp soil (gm) Empty mould Bulk density g/cc Container No Empty weight of container (gm) Container + wet soil (gm) Container + dry soil (gm) % water content
d
1+w
1
2
3
4
6611
6709
6835
6909
1936
2334
2160
2234
1972
2386
2386
2386
2386
2836
2.18
2.25
1..99
1.95
2.05
5
6647
13
15
486
04
208
9
8
12
8.8
16.22
16
19
24.4
14
17.98
14.6
18.3
22.6
13.1
4.25
7.44
11..1
13.1
15.42
1.87
1.9
1.96
1.99
1.73
8.0
b
kn/m3 Result:- 1) Maximum dry density of soil = 2.02 kn/m3 2) OMC = 11.8%
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Determination of California bearing ratio Aim :- To determine California bearing ratio of sub-grade soil. Apparatus :- Mould, steel cutting collar, spacer disc, surcharge weights, dial ganges, Is sieve of 4.75mm and 20mm Is sieve, miscellaneous scales, soaking tank, drying oven, filter paper, dishes and calibrating measuring jar. Procedure:Dynamically compacted specimen 1) Sieve the material through 20mm Is sieve 2) Take about 5kg of representative sample for fine grained soils and about 5kg for granular soils in mixing pan. 3) Add the water content equal to optimal moisture content. 4) Mix together the soil and water uniformly 5) Clamp the mould along with extension collar to base plate 6) Place the coarse filter paper on the top of the spacer disc. 7) Pour soil-water mix in the mould in such a quantity that after compaction about 1/3rd of the mould is filled. 8) Give 56 blows with rammer weighing 2.6kg falling through 310mm evenly spread on the surface. 9) Scratch the top layer of compacted surface Add more soil and compact
in similar fashion fill the mould completely in 5
layers 10)
Remove the extension collar and trim off the excess soil
by a straight edge. 11)
Remove the base plate, spacer disc and the filter paper
and not down the weight of mould and compacted specimen. 27
12)
Place a coarse filter paper on the perforated base plate.
13)
Invert the mould containing compacted soil and clamp it
to the base plate.
Soaking of specimen 1. Put a filter paper on the top of the soil and place the adjustable stem and perforated plate on the top of the filter paper. 2. Put annular weights to produce a surcharge equal to the weight of the base material and pavement expected in actual construction. Each 2.5kg weight is equivalent to 7cm of construction. A minimum 2 weight should be put. 3. Immerse the mould assembly and weights etc., in a tank of water allowing free access of water to the top and bottom of specimen. 4. Mount tripod of the specimen measuring device on the edge of the mould and not down the initial reading of dial gauge. 5. Keep the let-up undisturbed for 96 hours maintain constant water level. 6. Take the final reading at the end of period remove the tripod and take out mould allow to drain. 7. Remove the weights, perforated plate and top filter paper and weigh.
Penetration test. 1) Place the surcharge weights back on the top of the soaked soil specimen, place the assembly on the penetration test machine. 2) Seat the penetration piston at the centre of the specimen with the smallest possible load the full contact is established between the surface of the specimen and the piston. 28
3) Set the dial gauge and proving ring readings zero . apply load on penetration piston at 1.25mm/min. noted down the load at designated penetration. 4) At end detachet it form the penetration test.
Dry density by sand replacement method. Aim : - To determine the density of the given soil by replacement method.
sand
Apparatus:- Sand pouring cylinder, trowel or bent spoon cylindrical calibrating container, metal tray balance crucibles, oven, tongs, glass plate measuring jar. Procedure:1) Measure the internal volume of the caliberating container from the volume of water required to fill the container. 2) Fill the pouring cylinder with sand with in about 1 cm of the top and weigh it 3) Place the pouring cylinder connected on the top of caliberating container. 4) Open the shutter to allow the sand to run out and fill the caliberating cylinder. 5) When there is no further movement of sand in the pouring cylinder, close the shutter. 6) Remove the pouring cylinder on a plane surface such as glass plate. 7) Place the pouring cylinder on a plane surface such as glass plate. 8) Open the pouring cylinder on a plane surface such as glass plate. Where there is no movement of sand in the cylinder close the shutter. 9) Weigh the pouring cylinder with remaining sand. 29
Measurement of soil density 1) clean and level the ground where the liquid field density is required. 2) Fill the pouring cylinder with dry sand with in about 1 cm of the top and weigh it. 3) Place the metal tray with the central hole over the portion of soil to be tested. 4) Excavate the soil approximately 10cm dia and 15 cm deep with bent spoon. The hole in the tray will guide the dia of the hole to be made in the soil. 5) Collect the excavated soil in the metal tray weigh into the nearest gram. 6) Determine moisture content of excavated soil 7) Place the pouring cylinder covers the hole 8) Open the shutter and allow the sand to run out into the hole when there is no movement of sand the shutter is closed. 9) Remove the cylinder and weigh it. Observations:1) Size of pouring cylinder : 380mm ht ,115 mm dia. 2) Sand : passing 1.0mm retained on 0.6mm sieve.
Observation and Tabular column:
Caliberation :1 2 3 4 5
Initial mass of cylinder + sand (M1) gm Mass of pouring cylinder+ sand (before pouring in calibrating cylinder) (M2)gm Volume of caliberating container (cm3) Mass of cylinder + sand (M3) (after making a cone on level surface)(M3)gm Mass of sand to fill calibrating container only M4= M1 –2M2+M3 (gm) 30
7025 5150 1162.38 4850 7025-51504850=1575
6
Bulk density of sand b M1 (3) (g/cm3)
1575= 1.35g/cm3 1162.38
Density of soil in place 1 2 3 4 5 6 7 8
Mass tray + excavated soil (gm) Mass tray empty (gm) Mass excavated soil (M) (1) – (2) (gm) Mass cylinder + sand after pouring sand in hole (M4) gm Mass of sand in hole + cone = M1 – M4 (gm) Mass of sand in hole M” = M1 – M4 - M2 Volume of hole (V) = M”
sand
Bulk density of soil
M
V
Result:-
3
(g/cm )
1) Insitu density of soil = 1.7 g/cm3
31
3397 1738 1696 gms 7025 1749 1323 1323 =980 1.35 1696 = 1.7 980
32
Design of flexible pavement. Pavement is defined as relatively stable crust constructed over the natural soil for the purpose of supporting and disturbing the wheel loads and providing an adequate wearing surface. Depending on the mode of supporting and distributing loads, pavements are classified as flexible, rigid and semi flexible.
The flexible pavements consists of a relatively tin wearing surface built over a base course and sub-base course and they rest on compacted sub – grade . The flexible pavements are able to resist only very small tensile stresses.
Rigid pavements are made up of Portland cement concrete and may or may not have base course between the pavement and the sub-grade. A rigid pavement can take appreciable tensile stresses and is capable of bridging small weakness and depression in the sub-grade.
Semi flexible pavement. Is made of dry clean concrete or soil cement and possess qualities of intermediate between flexible and rigid pavements. A semi-flexible pavement possess appreciable flexural strength but its modulus of elasticity is considerably lower than that of concrete.
Design of pavement thickness by CBR method as per IRC recommendations 1) Given Data:Number of present commercial vehicles/day to be considered for designing the pavement 2) Obtained data form laboratory test :CBR (%) = 7.91% 33
= 650vehicles/day
Adopt : Adopt curve E in the graph. As its vehicle density ranges form 450-1500 vehicles/day Depth of construction in (mm) = 260 There for Adopt = 265 mm = 270 mm
Carpet
PREMIXED BITUMINOUS CARPET
20MM 75MM
WBM
GRADE 1 75MM
GRADE 2 GSB
GRANULAR SUB BASE
Pavement section by CBR Method
34
100MM
35
