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The hypothesis is that the comparable soil properties of lateritic soils such as Atterberg limits, specific gravity, optimum moisture content, maximum dry density, particle size distribution, unconfined compressive strength, and shear strength parameters, California bearing ratio would be accomplished for the soil samples collected at different depths. It is expected that the soil properties would be varying with depth, that is the sample collected at different depths will give different properties. It can be also contradicting in such a way that the soil properties may not vary with depth. This hypothesis would be test by experiments carried on lateritic soils and other types of soils mainly residual soil.
It has been mentioned earlier that the objectives of this project is to study the properties of lateritic soils within Mantin area. The method to be employed in this case study is simply to collect the samples of lateritic soils, classify them and study their strength properties such as shear strength parameters, unconfined compressive strength and California bearing ratio(CBR) .
Collection of soil samples
Preparation of sample
Particle size distribution
Compaction &CBR Test
Unconfined compressive strength
Direct Shear Box Test
Figure 3.1 summary of the research study
3.4 Material used in this study
3.4.1 Lateritic soil
Lateritic soils samples obtained at different depths within the Mantin area are study materials going to be used in this study. The samples would be collected following the British standards details of which are given in next section.
Type of laboratory tests
As mentioned earlier in chapter 1 that 12 tests would be carried out in this case study .These tests done to accomplish the objectives of this case study are, moisture content test, Atterberg limits(plastic limit and liquid limit)tests, specific gravity test, optimum moisture content, maximum dry density tests, sieve analysis test will be carried out according to British standards BS 1377-2:1990.The unconfined compressive strength of soil would be achieved by unconfined compression test based on guidelines given in BS 1377-7:1990.The shear strength parameters would be found through direct shear box test following BS 1377-7:1990. Optimum moisture content ,maximum dry density tests along with CBR testfollow BS 1377-4:1990 guidelines.
3.5.1 Moisture Content test
Moisture content also referred as water content is quantity of water in any soil. The ratio of mass of wet soil to mass of dry soil gives moisture content. The dry soil state relates to condition when there is no further reduction in amount of water at temperature not more than 110oC. The method mentioned here helps in determining the moisture content of a soil specimen as a percentage of dry mass of soil. This method is refereed as Oven -drying method based on BS 1377(part 2 1990) clause 3.2.
The apparatus and equipments used are complied with BS 1377-2:1990
Metal container resistant to corrosion for putting soil sample.
A (electronic) balance with accuracy of 0.01g to determine the weight of soil sample.
Drying oven, on which a temperature of 105 Â°C to 110 Â°C can be retained.
184.108.40.206 Test Apparatus
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Figure 3.2 Moisture Content Test Apparatus
The procedure mentioned below is in accordance with BS 1377-2:1990.
Measure the weight of clean and dry (empty) container on balance. Tag it as m1.
Put the soil sample to be tested in the container.
Weigh the container filled with soil, and record the weight again. Tag it as m2.
Place the container filled with soil in the oven for atleast 24 hours.
At last weigh the dry soil sample taken from oven including the container and record the weight. Tag it as m3.
220.127.116.11 Further guidelines:-
The estimated mass of soil sample needed for each main sample:
Fined grained soils = 30 g (weigh to 0.01 g)
Medium-grained soils = 300 g (weigh to 0.1 g)
Coarse-grained soils = 3,000 g or 3 kg (weigh to 1 g)
Remove the lid of container before placing it in oven.
Mass of empty container Â Â Â Â Â Â Â Â = m1 (g)
Mass of wet soil and container = m2 (g)
Mass of dry soil and container Â Â Â = m3 (g)
Mass of moisture loss in soil(after drying) = m2 - m3 (g)
Mass of dry soil sampleÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = m3 - m1 (g)
18.104.22.168 Sample calculation
Mass of empty container m1= 20.25 (g)
Mass of wet soil and container m2= 50.75(g)
Mass of dry soil and container m3= 47.25(g)
Mass of moisture loss in soil(after drying) m2 - m3= 3.50(g)
Mass of dry soil sample m3 - m1 = 27 (g)
Moisture content(w)=[(m2 - m3) / (m3 - m1)]Ã-100%=[(3.50 / 27)]Ã-100 %=12.96
3.5.2 Plastic limit test
The laboratory procedure for finding the plastic limit of soils is discussed in this section. This method is referred as small pyknometer method. The method mentioned here is in accordance BS 1377(part2, clause 5.3).
Plastic limit is the minimum moisture content at which soil i sin plastic state.
Flat glass plate for mixing soil
Flat glass plate to roll the threads
metal rod with diameter of 3 mm
drying oven and balance accurate to 0,01 (g)
22.214.171.124 Sample preparation
The soil is required for this test is 20g. The material passing the 425 Î¼m sieve is used.
Take 20 g of soil passing through 425 sieve or in natural state.
Put in glass plate and leave it for drying to some extent until it becomes enough plastic so that small balls can be formed.
Mould the soil ball between the fingers and roll it between the palms of the hands so that the heat generated by hands gradually dries it. The minor cracks will emerge on the surface. At this point split the ball into two equal portions of approximately 10g. Further divide each into four (can be more or less than four) equal parts.
Transform the soil .to 6mm diameter thread with first finger and thumb of both hands.
Roll the thread between the fingers of one hand and the surface of the glass plate by applying steady pressure. The pressure should be such that after five to ten back-and-forth movements of the hand, diameter of the thread should reduce from 6 mm to about 3 mm Some heavy clays may require more than this movements (10-15 movements. It is essential to keep a even rolling pressure throughout. There should not be reduction in rolling pressure as the thread diameter approaches 3 mm
Again take the soil mould it in fingers and repeat the process as mentioned above in steps 3-5.
.Do again step 4-6 until the thread crumbles when it has been rolled to 3-mm diameter. The metal rod acts as a reference for gauging this diameter
Plastic limit. is the first crumbling point . The pieces leftover after crumbling should not be combined together.
When the crumbling stage is achieved, collect the crumbled threads and put them into a weighed moisture content container
Apply same procedure for other three soil portions and get the moisture content by oven drying method. All the four portions of soil must be placed in same container to for measuring moisture content.
3.5.3 Liquid limit test.
The laboratory procedure for finding the liquid limit of soils is discussed in this section using the device called, Casagrande liquid limit apparatus with the single trial method. The point at which the consistency is altered from a plastic state to a liquid state is called liquid limit. It is denoted by (LL) or the moisture content of soil at border line between plastic limit and liquid limit is refereed as liquid limit.
This method is referred as One-point Casagrande method. The method mentioned here is in accordance BS 1377 (part2:, 1990, clause 4.6) .
Liquid limit deviceÂ (Casagrande's liquid limit device) shown in figure)Â Â
Two Spatulas or palette knives
A flat, glass plate, with thickness of 10mm about 500 mm square
Bottle or beaker, filled with distilled water
Apparatus for finding moisture content as mentioned earlier.
126.96.36.199 Adjustment of apparatus
The height of the liquid limit device should be such that when the cup of device is lifted to maximum height the 10mm gauge can nearly pass through the cup and base.
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Figure 3.3 Casagrande Liquid Limit Apparatus
Measure out about 100g of soil from soil sample under obsrevation.
Sieve it through the 425 Î¼m test sieve.(In regard to clay soil it can be removed by hand)
Put the soil specimen in glass plate and add distilled water.
Mix the paste and distilled water properly and intensively for at least 10 minutes.
Add the mixed paste of soil to the cup (resting at base) of liquid limit device and flatten the surface.
Split the soil into two equal parts with help of grooving tool. Move grooving tool from the hinge in the direction of the front in an uninterrupted circular movement. Grasp the grooving tool in such a way that it is perpendicular to the plane of the cup, and the chamfered edge facing the direction of movement.
Rotate the crank handle at the rate of 2 r/s in such a manner that the cup is lifted and dropped. At same time count the number of bumps. Continue turning the handle until the two parts of the soil meet at the bottom of the groove at the length of 13 mm, measured with the end of the grooving tool or with a ruler. Not down the number of bumps at which this closure takes place. The number shall be between 15 bumps and 35 bumps. .
Add a small amount of the prepared soil from the glass plate and mix it with the soil in the cup
Repeat the step 6 to step 9 until the closure of two parts occurs for same number of bumps for two repeated trials.
Take out the of the soil from the cup and put it in a appropriate container and find out its moisture content in accordance with oven drying method.
Moisture content of the test sample calculated as mentioned in earlier to the first decimal place.
Factor matching to the number of bumps which were recorded during test is found from table below.
Number of bumps
Number of bumps
Number of bumps
Number of bumps
Equation for calculating the liquid limit: - Liquid limit = moisture content Ã- factor
wL=w x factor
3.5.4 Plasticity index.
Plasticity index is difference of plastic limit and liquid limit.
Ip = wL - wp
3.5.5 Particle density (Specific gravity test).
The laboratory procedure for finding the particle density or specific gravity of soils is discussed in this section using the device called, small pyknometer. This method is referred as small pyknometer method. The method mentioned here is in accordance BS 1377(part2,clause 8.3)
Two density bottles of 50ml along with stoppers
Water bath with constant temperature(200C to 300C + 0.20C)
Vacuum desiccator along with protective cage.
Drying oven, on which a temperature of 105 Â°C to 110 Â°C can be maintained.
A (electronic) balance with an accuracy of 0.001g.
.Filter or vacuums pump.
Spatula or glass rod with specifications given in BS 1377-(part2,clause188.8.131.52)
Wash bottle containing distilled water free from air.
Rubber vacuum tubing.
First of all clean the density bottle along with stopper properly. Rinse it with acetone or mixture of alcohol -ether to dry it. Then pass warm air with temperature 105oC to 110oC through it.
Measure the weight of dried bottle and stopper with help of balance to 0.001g accuracy. Label it as (m1).
Add the one of the soil specimens to the density bottle again weigh it on the balance. Label it as (m2).
Add air- free distilled water to soil in density bottle, nearly covering it.
Put the density bottle along with its contents(soiland distilled water covering it), but without stopper in the vacuum desiccator. Decrease the pressure slowly to about 20 mm of mercury. Leave the bottle for at least 1 hour under vacuum until no further loss of air is noticeable .
Discharge the vacuum and take out the lid of desiccator. Stir the soil in the bottle with help of spatula ,vibrating the bottle or stirring rod. Before removing the stirring rod or spatula wash off any soil particles with a few drops of air-free water. Put back the lid of the desiccator and do again the vacuum procedure as mentioned earlier.
This procedure is repeated until no further air is emitted from the soil.
Take out the density bottle from the desiccator and add extra air-free water until full. Put in the stopper and immerse the bottle up to the neck in the constant-temperature bath. Leave the bottle in the bath for at least 1 hour so that the bottle reaches the temperature of the bath.
Remove the stopper and add extra liquid to fill the bottle If there is an apparent decrease in the volume of the liquid. Replace the stopper .Again place the bottle for bath and allow the contents to achieve the constant temperature..
Take out the bottle from the bath and dry it by wiping. Weigh the bottle with stopper, soil and water to 0.001g .Label it as (m3)
11)Clean out each bottle, fill it completely with de-aerated water, put it in bath as mentioned before - Take the bottle out of the bath, wipe it dry and weigh it to the nearest 0.001g (m4)
M1 = mass of density bottle
M2 = mass of bottle and dry soil
M3 = mass of bottle and soil and liquid
M4 = mass of bottle and liquid
If the difference between particle density of two specimens is more than 0.03Mg/m3 the test shall be repeated.
3.5.6Particle Size Distribution
This is a section includes the procedure for finding the grain size of a soil. This test method is known as sieve analysis method.. The sieve analysis includes the dry sieving and the wet sieving. Here we discuss the dry sieving. The test is carried out on BS 1377 (part2,1990)
The set of apparatus required for this task include
Pile the sieves with different hole sizes (ranging from 75mm to 63Î¼m)
Balance for weighing the soil with decimal reading up to 0.01g.
Oven for drying.
A mechanical sieve shaker..
184.108.40.206 Test Procedure
The sample of the soil dried by oven and 500g of it is taken.
Remove any lumps in sample.
Find out the mass of the sample label it (Wt) in grams.
Place sieves with the larger opening sizes at the top followed by smaller opening sized sieves
Put the soil in the top most sieve of the stack .
Put the cover and set it in the sieve vibrator, the clamps should be tightened properly. Turn the shaker on for at least 5 to 10 minutes.
Take it out at the end of the time set to vibrate, each sieve aperture + retained soil from the top sieve to the pan should be weighed. The percentage passing the 63Î¼m is checked by the weighing the amount in the receiver.
Record all the weight in a result sheet.
3.5.6 Direct shear test
The laboratory procedure for determining the shear strength, cohesion and angle of shearing resistance (angle of internal friction) of soils is discussed in this section. This method is referred as shear box method. The method mentioned here is in accordance BS 1377(part7 1990, clause 4).
The shear strength is one of the most significant engineering properties of a soil, because it is necessary and needed whenever a structure is dependent on the soil's shearing resistance. The shear strength is required for engineering purposes such as finding the stability of slopes, calculating the pressure exerted by a soil on a retaining wall and to find the bearing capacity for foundations etc.
The maximum resistance of soil to shearing stresses is said to shear strength of soil. Soil is made up of individual particles that can slide over and roll relative to one another. Shear strength of a soil is equivalent to the highest value of shear stress that can be mobilized within a soil mass without failure happening.
Shear box with clamping screws
Grid plates (serrated and perforated)
Deformation dial gauges
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Figure 3.4 Direct Shear Test Apparatus
Determine shear box dimensions, set up the box by fixing its upper part to the lower part with clamping screws, and then place a porous stone at the base.
For undrained tests, place a serrated grid plate on the porous stone with the serrations at perpendicular to the direction of shear. For drained tests, use a perforated grid over the porous stone.
Put the soil(saturated) into the shear box in three layers and for each layer apply a controlled amount of tamping with a tamper. Place the upper grid plate, porous stone and loading pad in sequence on the soil specimen..
Place the box inside its container and mount it on the loading frame. Bring the upper half of the box in contact with the horizontal proving ring assembly.
Complete the assembly, remove the clamping screws from the box, and initialize the horizontal displacement gauge, vertical displacement gauge and proving ring gauge to zero.
Set the vertical normal load to a predetermined value(10kg,30kg,50kg)..For drained tests, allow the soil to consolidate fully under this normal load. Avoid this step for undrained tests.
Start the motor with a selected speed. Continue taking readings of the gauges until the horizontal shear load peaks and then falls.
.Repeat the test on the same specimen under different normal load values(10kg,30kg,50kg )
Change the dial gauge readings to the suitable displacement(multiply by 0.002mm).
Use proving ring reading in suitable equation of force vs. dial gauge reading graph to get force and than convert force into shear stress.
Plot the shear stress versus horizontal displacement. Read the maximum value of shear stress if failure has happen.
Find maximum shear stress for each value of load.
Also convert normal load to normal stress.
Plot the maximum shear stress versus the corresponding normal stress for each test and get the y intercept of best fit straight line it cohesion C' and the angle of line is angle of internal friction
220.127.116.11 Sample calculation
Horizontal guage (1/100)
Force = mx + c
Where x is the value of proving ring reading.
c = 0
mx=0.0048 x ..............................................................................(from the graph )
Similarly we find for all samples.
Normal stress corresponding to 10 kg
10Ã-9.81/1000*0.0036= 27.25 KN/m2
Similarly we find for 30kg and 50kg .
3.5.7 Unconfined compressive strength test
The laboratory procedure for determining the unconfined compressive strength of soils is discussed in this section. This method is referred as definitive method or load frame method .The method mentioned here is in accordance BS 1377(part7 1990, clause7.2).
Unconfined compression testing machine:-
Machine can be manual (operated by a person) or automatic (motorized machine) but should have capability of applying axial compression to soil specimen at a desired and appropriate rate.
Dial gauge with accuracy of 0.01mm to measure the axial compression of soil specimen.
Force measuring tool. It can be load ring or any other device depending on strength of soil specim
Two flat platens:-Through which the axial force is passed onto soil specimen. Their diameter can be same as that of soil specimen on larger than it.
Timer (stopwatch):-Readable to 1 s.
Balance with an accuracy of 0.1 g.
Apparatus for determination of moisture content based upon the clause 3.2 of BS 1377-2:1990.
Find out the mass of the test specimen to the nearest 0.1 g.
Determine the length and diameter of the soil specimen to the nearest 0.1mm.
Take minimum 3 reading and hence calculate average value of dimensions.
Position the specimen on the pedestal in such a way that it should be in centre of the compression machine and between the upper and lower platens. There should not be loss in moisture content of soil and the specimen of soft soil should be given due attention so that it does not disturb.
Adjust the dial of axial deformation gauge to zero or a suitable initial reading.
Note down the initial readings of the force and compression gauges
Decide suitable a rate of axial deformation .The rate of axial strain should not go beyond 2 %/min
Apply compression to the soil specimen at the chosen rate and note down corresponding readings of the force-measuring device and the axial deformation gauges at regular intervals of compression. For example take at least 12 sets of readings in order to characterize the stress-strain curve for 0.5 % strain.
Carry on the test until the maximum value of the axial stress is crossed, or the axial strain reaches 20 %.
Take out the load from the specimen and record the final reading of the force measuring gauge to verify the initial reading.
Create a sketch of the test specimen to specify its type of failure.
Determine the moisture content of specimen in accordance with BS 1377(part2, clause 3.2)
Axial strain ( =Î”L/Î”Lo
Î”L= change in length of specimen shown by axial deformation gauge(in mm)
Lo is the initial length of the specimen (in mm).
Compute the force, P (in Newton, N), applied to the specimen for each set of readings by multiplying the change in reading of the force-measuring device from zero load (in divisions of digits) by the appropriate load calibration factor (in N/division or N/digit).
Axial compressive stress ,kPa) is calculated for all the set of reading by equation
Where Ao is the initial cross-sectional area of specimen (in millimetres, mm)
Draw the stress-strain curve through the points obtain by plotting values of compressive stress as ordinates against corresponding values of strain(in percentage) as abscissae.
Determine the point on the graph demonstrating the failure condition, which is the point at which the maximum compressive stress sustained by the specimen takes place, or the point related to a strain of 20 % if that comes first.
By means of that point, find out the compressive stress in the specimen at failure, known as the unconfined compressive strength, qu (in kPa)
Establish the axial strain of the specimen at failure.
Figure 3.5 Unconfined Compressive strength machine
3.5.8 Compaction test
The test procedure mentioned in this section is in accordance with BS 1377Part 4-1990 .The solid particles are held more firmly and kept intact by compaction which is generally achieved by mechanical method .Compaction process also increases the dry density of the soil. The level of compaction applied and the quantity of water present in the soil the effect the dry density of soil. Dry density attains a maximum value and moisture content known as optimum moisture content.
2.5 kg hammer with 50mm face diameter (light manual method)
4.5 kg hammer with 50mm face diameter (Heavy manual method).
Apparatus for taking out soil sample from mould.
Balance with accuracy of 5 g.
Weigh the mould with help of balance = m1
Put in loose soil to the mould.
Position the guide tube tenderly on the soil and grasp it upright.
27 blows for the 1 L mould and 62 blows for the CBR mould for soil compaction
The blows should be widely spread on soil surface not hitting single point.
Put another layer almost equal to first one and give blows as above. Similarly do for third ,fourth and fifth layer.
.Take out the extension collar cautiously and remove the surplus soil and level off the top of the mould. Fine material should be added to small cavities, formed by the removal of stones,
Weigh the soil + mould and label it as (m2).
Take out the sample from mould mix with it with prepared soil and added different amount of water. For cohesive soils add 100-200 ml and sandy-gravel 50-100 ml of water to 5kg soil.
Do the compaction process as described previously.
Average moisture content, W %, for all specimens
Dry density corresponding to moisture content:
Draw a graph by plotting moisture contents and their corresponding dry densities .Join the point that give a best curve. Maximum point on this curve and find the moisture content and density relative to this point. This will be optimum moisture content and maximum dry density.
3.5.9 California bearing test.
This method described in this section is to determine of the California Bearing Ratio (CBR) of soil in laboratory in accordance with BS 1377 (part 4,1990).
California bearing ratio depicts bearing capacity of soil and is important parameter in pavement design.
Motorized compression machine (penetration rate of 1 mm/min).
Device for measuring load..
Device to measure displacement ( range 25 mm ,scale units 0.01 mm).
Balance,: (With capacity of weighing 25 kg with accuracy of 5 g.
Oven for drying (maintaining temperature 105-110oC
Connect load-measuring device to the compression machine.
Plunger with cylindrical shape, diameter 49,5 mm ,cross-sectional area of 1935 mm2 and a length of 250 mm, is linked to the load-measuring device.
The mould with the soil sample and the surcharge weights is positioned in the machine.
The plunger should be placed at top of the specimen - .
Adjust the displacement-measuring device to initial reading of zero.
begin the loading, at rate of 1 mm/min.
At every 0.25 mm displacement note down the reading from load-measuring device.
At 7.5 mm penetration, the machine can be switched off.
Determine the moisture content of the mould.
The readings from the test have to be plotted in a load penetration diagram.
The load corresponding to 2.5 mm and 5.0 mm penetration has to be interpreted from this diagram.
Get the CBR value from standard test.
5) The similar calculation is made for 5 mm penetration.
6) The larger of the two is then the CBR-value.