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DEPARTMENT OF CIVIL ENGINEERING

GEOTECHNICAL ENGINEERING II LABORATORY MANUAL

1

For Final Year Civil Engineering Degree Students

Of

RAJIV GANDHI PROUDYOGIKI VISHWAVIDYALAYA, BHOPAL

Practical Journal

Of

Geotechnical Engineering II (CE-801)

CIVIL ENGINEERING DEPARTMENT

PRESTIGE INSTITUTE OF ENGINEERING & SCIENCE

PIES, INDORE

Name:

Year: Branch: Semester:

Roll No.: University Roll No.:

Date of Submission.:




2

List of Experiments

S. NO. TITLE PAGE NO. DATE OF

EXP.

DATE OF

SUB.

TEACHERS

SIGNATURE

1. FIELD DENSITY TEST BY CORE CUTTER

METHOD

2. FIELD DENSITY TEST BY SAND

REPLACEMENT METHOD

3. DIRECT SHEAR TEST

4. CBR (STUDY)

5. PLATE LOAD TEST (STUDY)

6. UNCONFINED COMPRESSION TEST

7. STANDARD PENETRATION TEST (STUDY)

8. DENSITY TEST

9. VANE SHEAR TEST

10. UNDRAINED TRI-AXIAL TEST

11. PROCTER COMPACTION TEST




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EXPERIMENT-01

DENSITY OF SOIL BY CORE CUTTER METHOD

AIM OF THE EXPERIMENT:

To determine the field or in-situ or bulk density or unit weight of soil by core cutter method

APPARATUS REQUIRED:

1. Cylindrical core cutter

2. Steel rammer

3. Steel dolly

4. Balance of capacity5 Kg and sensitivity 1 gm.

5. Balance of capacity 200gms and sensitivity 0.01gms.

6. Scale

7. Spade or pickaxe or crowbar

8. Trimming Knife

9. Oven

10. Water content containers

11. Desiccator.

THEORY:

Field density is defined as weight of unit volume of soil present in site. That is

= W

V

Where, = Bulk density of soil, W = Total mass of soil & V = Total volume of soil

The soil weight consists of three phase system that is solids, water and air. The voids may be

filled up with both water and air, or only with air, or only with water. Consequently the soil may

be dry, saturated or partially saturated. In soils, mass of air is considered to be negligible, and

therefore the saturated density is maximum, dry density is minimum and wet density is in between

the two.

Dry density of the soil is calculated by using equation,

=

1 + w

Where, = dry density of soil , = bulk density of soil, w = moisture content of soil.




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The equipment arrangement of core cutter method is shown as fallows,

PROCEDURE:

1. Measure the height and internal diameter of the core cutter.

2. Weight the clean core cutter.

3. Clean and level the ground where the density is to be determined.

4. Press the cylindrical cutter into the soil to its full depth with the help of steel rammer.

5. Remove the soil around the cutter by spade.

6. Lift up the cutter.

7. Trim the top and bottom surfaces of the sample carefully.

8. Clean the outside surface of the cutter.

9. Weight the core cutter with the soil.

10. Remove the soil core from the cutter and take the representative sample in the water content

containers to determine the moisture content

OBSERVATION AND CALCULATION TABLE:

Internal diameter of cutter (cm): _ _ _ _ _ _ _ _

Height of the cutter (cm): _ _ _ _ _ _ _ _

Cross sectional area of the cutter (cm2): _ _ _ _ _ _ _ _

Volume of the cutter, V (cm3): _ _ _ _ _ _ _ _

Water/Moisture content determination:




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sample 1 sample 2 sample 3

Weight of can, W1 (g)

Weight of can + wet soil W2 (g)

Weight of can + dry soil W3 (g)

Water/Moisture content w% =

x100

Calculation Table:

sample 1 sample 2 sample 3

Mass of core cutter, W1 (gm)

Mass of cutter + soil from field, W2

(gm)

Bulk density, (gm/cm3)

= W W

V

Dry density , (gm/cm3)

=

1 +w

PRECAUTIONS:

1. Steel dolly should be placed on the top of the cutter before ramming it down into the ground.

2. Core cutter should not be used for gravels, boulders or any hard ground.

3. Before removing the cutter, soil should be removed around the cutter to minimize the

disturbances.

4. While lifting the cutter, no soil should drop down.

APPLICATION:

Field density is used in calculating the stress in the soil due to its overburden pressure it is needed

in estimating the bearing capacity of soil foundation system, settlement of footing earth pressures

behind the retaining walls and embankments. Stability of natural slopes, dams, embankments and

cuts is checked with the help of density of those soils. It is the density that controls the field

compaction of soils. Permeability of soils depends upon its density. Relative density of

cohesionless soils is determined by knowing the dry density of soil in natural, loosest and densest

states. Void ratio, porosity and degree of saturation need the help of density of soil.




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EXPERIMENT-02

SAND REPLACEMENT METHOD

OBJECTIVE

Determine the in situ density of natural or compacted soils using sand pouring cylinders.

NEED AND SCOPE.

The in situ density of natural soil is needed for the determination of bearing capacity of soils, for

the purpose of stability analysis of slopes, for the determination of pressures on underlying strata

for the calculation of settlement and the design of underground structures.

It is very important quality control test, where compaction is required, in the cases like

embankment and pavement construction.

APPARATUS REQUIRED

1. Sand pouring cylinder of 3 litre capacity, mounted above a pouring cone and separated by a shutter cover plate.

2. Tools for excavating holes; suitable tools such as scraper tool to make a level surface. 3. Cylindrical calibrating container with an internal diameter of 100 mm and an internal

depth of 150 mm fitted with a flange 50 mm wide and about 5 mm thick surrounding the

open end.

4. Balance to weigh unto an accuracy of 1g. 5. Metal containers to collect excavated soil. 6. Metal tray with 300 mm square and 40 mm deep with a 100 mm diameter hole in the

centre.

7. Glass plate about 450 mm square and 10mm thick. 8. Clean, uniformly graded natural sand passing through 1.00 mm I.S.sieve and retained on

the 600micron I.S.sieve.

9. Suitable non-corrodible airtight containers. 10. Thermostatically controlled oven with interior on non-corroding material to maintain the

temperature between 1050C to 110

0C.

11. Dessicator.

THEORY

By conducting this test it is possible to determine the field density of the soil. The moisture

content is likely to vary from time and hence the field density also. So it is required to report the

test result in terms of dry density. The relationship that can be established between the dry density

with known moisture content is as follows:

=

Where, = dry density of soil

= bulk density of soil




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w = moisture content of soil.

PROCEDURE

Calibration of the Cylinder

1. Fill the sand pouring cylinder with clean sand so that the level of the sand in the cylinder is

within about 10 mm from the top. Find out the initial weight of the cylinder plus sand (W1) and

this weight should be maintained constant throughout the test for which the calibration is used.

2. Allow the sand of volume equal to that of the calibrating container to run out of the cylinder by

opening the shutter, close the shutter and place the cylinder on the glass. Sand takes place in the

cylinder close the shutter and remove the cylinder carefully. Weigh the sand collected on the glass

plate. Its weight (W2) gives the weight of sand filling the cone portion of the sand pouring

cylinder.

Repeat this step at least three times and take the mean weight (W2) Put the sand back into the sand

pouring cylinder to have the same initial constant weight (W1)

Determination of Bulk Density of Soil

3. Determine the volume (V) of the container be filling it with water to the brim. Check this

volume by calculating from the measured internal dimensions of the container.

4. Place the sand poring cylinder centrally on the calibrating container making sure that constant

weight (W1) is maintained. Open the shutter and permit the sand to run into the container. When

no further movement of sand is seen close the shutter, remove the pouring cylinder and find its

weight (W3).

Determination of Dry Density of Soil in Place

5. Approximately 60 cm2 area of soil to be tested should be trimmed down to a level surface,

approximately of the size of the container. Keep the metal tray on the level surface and excavate a

circular hole of volume equal to that of the calibrating container. Collect all the excavated soil in

the tray and find out the weight of the excavated soil (Ww).Remove the tray, and place the sand

pouring cylinder filled to constant weight so that the base of the cylinder covers the hole

concentrically. Open the shutter and permit the sand to run into the hole. Close the shutter when

no further movement of the sand is seen. Remove the cylinder and determine its weight (W4).

6. Keep a representative sample of the excavated sample of the soil for water content

determination.




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OBSERVATIONS AND CALCULATIONS

S. No. Sample Details Calibration 1 2 3

1. Volume of calibrating container (V) in cc

2. Weight of sand + cylinder before pouring W1 gm

3. Weight of sand + cylinder after pouring W3 gm

4. Weight of sand in cone (of pouring cylinder) W2 gm

5.

Weight of sand to fill calibrating containers

Wa = (W1-W3-W2) gm

6. Bulk density of sand s = Wa/V (gm/cc)

S. No. Measurement of Soil Density 1 2 3

1. Weight of wet soil from hole Ww gm

2. Weight of sand + cylinder before pouring W1 gm

3. Weight of sand + cylinder after pouring W4 gm

4. Weight of sand in hole Wb = (W1-W2-W4) gm

5. Bulk density b = (Ww /Wb)* s gm/cc

S. No. Water content determination 1 2 3

1. Container number

2. Weight of wet soil

3. Weight of dry soil

4. Moisture content (%)

5. Dry density d = b / (1+w) gm/cc

GENERAL REMARKS

1. While calibrating the bulk density of sand, great care has to be taken.

2. The excavated hole must be equal to the volume of the calibrating container.




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EXPERIMENT-03

DIRECT SHEAR TEST

OBJECTIVE

To determine the shear parameters of a sandy soil specimen by direct shear test.

THEORY

Shear strength of a soil is its maximum resistance to shearing stresses. The shear strength is

expressed as

S = c+ tan

Where c=effective cohesion; = effective stress; and =effective angle of shearing resistance.

The shear tests can be conducted under three different drainage conditions. The direct shear test is

generally conducted on sandy soils as a consolidated drained test.

EQUIPMENT

(1) Shear box, divided into two halves by a horizontal plane, and fitted with locking and spacing

screws; (2) Box container to hold the shear box; (3) Base plate having cross grooves on its top

surface; (4) grid plates, perforated, 2nos.; (5) Porous stones, 6mm thick, 2nos; (6) Loading pad;

(7) Loading frames; (8) Loading yoke; (9) Proving ring, capacity 2kN; (10) Dial gauges, accuracy

0.01 mm, 2nos.; (11) Static or dynamic compaction device; (12) Spatula.

PROCEDURE

1. Measure the internal dimensions of the shear box. Also determine average thickness of the

grid plates.

2. Fix the upper part of the box to the lower part by using the locking screws. Attach the

base plate to the lower plate.

3. Place the grid plate in the shear box keeping the serration of the grid at the right angles to

the direction of shear. Place a porous stone over the grid plate.

4. Weigh the shear box with shear plate, grid plate and the porous stone.

5. Place the soil specimen in the box. Tamp it directly in the shear box at the required

density. When the soil in the top of the shear box is filled upto 15 mm depth, level the soil

surface.

6. Weigh the box with the soil specimen.

7. Place the box inside the box container, and fix the loading pad o the box. Mount the box

container on the loading frame.

8. Bring the upper half of the box in the contact with the proving ring. Check the contact by

giving a slight movement.

9. Fill the container with the water if the soil is to be saturated; otherwise omit this step.

10. Mount the loading yoke on the ball placed on the loading pad.




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11. Mount one dial guage on the loading yoke to record the vertical displacement and another

dial guage on the container to record the horizontal displacement.

12. Place the weight on the loading yoke to apply normal stress of 25 kN/m. Allow the sample

to consolidate under the applied normal stress. Note the reading of the vertical

displacement dial guage.

13. Remove locking screws. Using the spacing screws, raise the upper part slightly above the

lower part such that the gap is slightly larger than the maximum particle size.

14. Adjust all the dial guage to read zero. The proving ring should also be zero.

15. Apply the constant shear load at a constant rate of 0.2 mm/minute.

16. Record the readings of the proving ring, the vertical displacement dial guage and the

horizontal displacement dial guage at the regular time interval. Take the few readings at

the closer intervals.

17. Continue the test till the specimen fails or till a strain of 20% is reached.

18. At the end of the test, remove the specimen from the box, and take a representative sample

for the water content determination.

19. Repeat the test on the identical specimens under the normal sresses of 50, 100, 200, 400

kN/m, etc.(The range of stresses selected should correspond to the actual field condition).

DATA SHEET FOR DIRECT SHEAR TEST

Size of the box = Area of the box =

Thickness of the specimen = Volume of the specimen =

Mass of soil specimen = Bulk density =

Water content = Dry density =

Void ratio = Tare mass of hanger =

Mass on hanger = Total mass =

Normal stress =

Mass of the box + base plate + porous stone + grid plate =

Mass of the box + base plate + porous stone + grid plate + soil specimen =




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Observations Calculations

S.No. Elapsed

time

Horizontal

dial guage

Vertical

dial

guage

Proving

ring

Shear

displacement

Vertical

displacement

Shear

force

Shear

stress

Use separate data sheet for tests under different normal stresses. Determine the shear stress at

failure in each case. Summarise the results as follows.

Test No. Normal Stress

kN/m2

Shear Stress

at failure

kN/m2

Shear

displacement

at failure

Initial water

content

Final water

content

1

2

3

4

5

25

50

100

200

400

Plot the coloumb envelop between the normal stress as abscissa and shear at failure as ordinate.

RESULT

From the plot, c = =




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EXPERIMENT-04

LABORATORY C.B.R. TEST APP. (California Bearing Test)

OBJECTIVE

To determine the CBR value of a given soil specimen.

THEORY

The California Bearing Ratio (CBR) test was developed by the California Division of Highway as

a method of classifying and evaluating soil-sub grade and base course materials for flexible

pavements. Just after World War II, the U.S. Corps of Engineers adopted the CBR test for use in

designing base course for airfield pavements. The test is empirical and results can not be related

accurately with any fundamental property of the material. The method of test has been

standardized by the ISI also.

The CBR is a measure of resistance of a material to penetration of standard plunger under

controlled density and moisture conditions. The test procedure should be strictly adhered if high

degree of in the laboratory. U.S. Corps of Engineers have also recommended a test procedure for

in-situ test. Many methods exist today which utilize mainly CBR test values for designing

pavement structure. The test is simple and has been extensively investigated for field co relations

of flexible pavement thickness requirement.

Briefly, the test consists of causing a cylindrical plunger f 50mm diameter to penetrate a pavement

component material at 1.25mm/minute. The loads, for 2.5mm and 5 mm are recorded. This load is

expressed as percentage of standard load value at a respective deformation level to obtain CBR

value. The standard load values were obtained from the average of large number of tests on

different crushed stones and are given in table.

Standard Load Values on Crushed Stones for Different Penetration Values

Penetration, Standard Unit standard

mm Load kg. load, kg/cm2

--------------------------------------------------------------------------- 2.5 1370 70 5.0 2055 105 7.5 2630 134 10.0 3180 162 12.5 3600 183

Apparatus: (a) Loading Machine:

Any compression machine which can operate at a constant rate of 1.25mm per minute can be used

for this purpose. If such machine is not available then a calibrated hydraulic press with proving




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ring to measure load can be used. A metal penetration piston or plunger of diameter 50mm is

attached to the loading machine.

(b) Cylindrical Moulds:

Moulds of 150mm diameter and 175mm height provided with a collar of about 50 mm length and

Detachable perforated base are used for this purpose. A spacer disc of 148mm diameter and

47.7mm thickness is used to obtain specimen of exactly 127.3mm height.

(c) Compaction Rammer:

The material is usually compacted as specified for the work, either by dynamic compaction or by

static compaction.

(d) Adjustable stem, perforated plate, tripod and dial gauge:

The standard procedure requires that the soil sample before testing should be soaked in water to

measure swelling. For this purpose the above listed accessories are required.




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(e) Annular weight:

In order to simulate the effect of the overlying pavement weight, annular weights each of 2.5 kg

weight and 147mm diameter are place on the top of the specimen, both at the time of soaking and

testing the samples, as surcharge. Besides above equipment, coarse filter paper, sieves, oven,

balance, etc. are required.

Procedure:

As per the ISI, the CBR test may be performed either on undisturbed soil specimens obtained by

fitting a cutting edge to the mould or on remolded specimens. Remolded soil specimens may be

compacted either by static compaction or by dynamic compaction. When static compaction is

adopted, the batch of soil is mixed with water to give the required moisture content; the correct

weight of moist soil to obtain the desired density is placed in the mould and compaction is

attained by pressing in the spacer disc using a compaction machine or jack. The preparation of soil




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specimens by dynamic compaction or ramming is more commonly adopted and is explained

below. About 45 kg. Of material is dried and dived through 20mm sieve. If there is note worthily

proportion of materials retained on 20mm sieve, allowance for larger size materials is made by

replacing it by an equal weight of material passing 20mm sieve and retained on 4.75mm sieve.

The optimum moisture content and maximum dry density of the soil are determined by adopting

either IS light compaction (Proctor compaction) or IS heavy compaction (modified Proctor or

modified AASHO compaction) as per the requirement. Each batch of soil (of at least 5.5 kg

weight for granular soils and 4.5 to 5.0 kg weight for fine grained soils) is mixed with water up to

the optimum moisture content or the field moisture content if specified so. The spacer disc is

placed at the bottom of the mould over the base plate and a coarse filter paper is placed over the

spacer disc. The moist soil sample is to be compacted over this in the mould by adopting either the

IS light compaction or the IS heavy compaction.

CALIFORNIA BEARING RATIO TEST

(i) For IS light compaction or proctor compaction, the soil to be compacted is divided into three

equal parts; the soil is compacted in three equal layers, each of compacted thickness about 44mm

by applying 56 evenly distributed blows of the 2.6 kg rammer.

(ii) For IS heavy compaction or the modified proctor compaction, the soil is divided into five

equal parts; the soil is compacted in five equal layers, each of compacted thickness about 26.5mm

by applying 56 evenly distributed blows of the 4.89 kg rammer. After compacting the last layer,

the collar is removed and the excess soil above the top of the mould is evenly trimmed off by

means of the straight edge. It is important to see if the excess soil to be trimmed off while

preparing each specimen is of thickness about 5.0mm; if not the weight of soil taken for

compacting each specimen is suitably adjusted for the repeat tests so that the thickness of the

excess layer to be trimmed off is about 5.0mm. Any hole that develops on the surface due to the

removal of coarse particles during trimming. May be patched with smaller size material. Three

such compacted specimens are prepared for the CBR test. About 100 g of soil samples are

collected from each mould for moisture content determination, from the trimmed off portion. The

clamps are removed and the mould with the compacted soil is lifted leaving below the perforated

base plate and the spacer disc which is removed. The mould with the compacted soil is weighed.

A filter paper is placed on the perforated base plate, the mould with compacted soil is inverted and

placed in position over the base plate (such that the top of the soil sample is now placed over the

base plate) and the clamps of the base plate are tightened. Another filter paper is placed on the top

surface of the sample and the perforated plate with adjustable stem is placed over it. Surcharge

weight of 2.5 or 5.0kg weight are placed over the perforated plate and the whole mould with the

weights is placed in a water tank for soaking such that water can enter the specimen both from the

top and bottom. The swell measuring device consisting of the tripod and the dial gauge are placed

on the top edge of the mould and the spindle of the dial gauge is placed touching the top of the

adjustable stem of the perforated plate. The initial dial gauge reading is recorded and the test set

up is kept undisturbed in the water tank to allow soaking of the soil specimen for four full days or




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96 hours. The final dial gauge reading is noted to measure the expansion or swelling of the soil

specimen due to soaking. The swell measuring assembly is removed, the mould is taken out of the

water tank and the sample is allowed to drain in a verticle position for 15 minutes. The surcharge

weights, the perforated plate with stem and the filter paper are removed. The mould with the soil

sample is removed from the base plate and is weighed again to determine the weight of water

absorbed. The mould with the specimen is clamped over the base plate and the same surcharge

weights are placed on the specimen centrally such that the penetration test could be conducted.

The mould with base plate is placed under the penetration plunger of the loading machine. The

penetration plunger is seated at the centre of the specimen and is brought in contact with the top

surface of the soil sample by applying a seating load of 4.0kg. The dial gauge for measuring the

penetration values of the Plunger is fitted in position. The dial guage of the proving ring (for load

reading) and the penetration plunger at a uniform rate of 1.25mm / min. The load readings are

recorded at penetration reading of 0.0, 0.5, 1.0, 1.5, 2.5, 3.0, 4.0, 5.0, 7.5, 10.0 and 12.5mm. In

case the load readings start decreasing before 12.5mm penetration, the maximum load value and

the corresponding penetration value are recorded. After the final reading, the load is released and

the mould is removed from the loading machine. The proving ring calibration factor is noted so

that the load dial values can be converted into load in kg. About 50 g of soil is collected from the

top three cm depth of the soil sample for the determination of moisture content.

Calculation:

The swelling or expansion ratio is calculated from the observations during the swelling test using

the formula:

Expansion ratio = 100 (df - di) / h

Where:

df = Final dial gauge reading after soaking, mm

di = Initial dial gauge reading before soaking, mm

h = Initial height of the specimen, mm.

The load values noted for each penetration level are divided by the area of the loading plunger

(19.635 cm2) to obtain the pressure or unit load values on the loading plunger. The load

penetration curve is then plotted in natural scale for each specimen as shown in. If the curve is

uniformly convex upwards as shown for specimen no. 1, no correction is needed. In case there is a

reverse curve or the initial portion of the curve is concave upwards as shown for specimen no.2,

necessity of a correction is indicated. A tangent is drawn from the steepest point on the curve to

intersect the base at point Y which is the corrected origin corresponding to zero penetration. The

unit load values corresponding to 2.5 and 5.0mm penetration values (either from the original

origin for curve without correction or from the corrected origin for the curve with correction, as

the case may be) are found from the graph. The

CBR value is calculated from the formula:

Unit load carried by soil sample at defined penetration level




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CBR, Percent = ------------------------- X 100

Unit load carried by standard crushed stones at above penetration level

The unit load values on standard stones are given in

The expansion ratio of soil due to soaking and the other details of the test may be reported as

given in the observation sheet. The CBR values at 2.5mm and 5.0mm penetrations are calculated

for each specimen from the corresponding graphs. Generally the CBR value at 2.5mm penetration

is higher and this value is adopted. However if higher CBR value is obtained at 5.0mm

penetration, the test is to be repeated to verify the results; if the value of the soil sample.The

average CBR value of three specimens is reported to the first decimal place. According to the

Indian Roads Congress, if the maximum variation in laboratory in CBR values between the three

specimens exceeds the value given below for the different ranges, the CBR tests should be

repeated on additional three specimens and the average value of six specimens is adopted.




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Maximum permissible variation

in CBR values, %

Range of CBR

Values, %

3.0

5.0

10.0

Not

Significant

Up to 10

10 to 30

30 to 60

above 60

Discussion:

Undisturbed soil sample may be used for the CBR test by taking out samples from the field in the

mould by attaching a core cutter. Due to high degree of disturbance in sample, this method is

generally not adopted. The CBR test is essentially an arbitrary strength test and hence can not be

used to evaluate the fundamental soil properties. Unless the test procedure is strictly followed,

dependable results cannot be obtained. The compaction specifications such as total height of

compacted specimen (before trimming off), the equality of thickness of the five compacted layers

and the uniformity of distribution the blows of the rammer in each layer (in the case of dynamic

compaction) affect the test results. The initial upward concavity of the load- penetration curve

calling for the correction may be due to (i) piston surface not being fully in contact with top of the

specimen or (ii) the top-layer of soaked soil being too soft. The test is meant only for soil and

granular base course materials and hence may not be suitable for semi-rigid materials like soil-

cement.




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EXPERIMENT-05

VERTICAL PLATE LOAD TEST

OBJECT- To conduct vertical plate load test in the field and determine allowable soil pressure of

soil foundation system.

APPARATUS-

(1) Square or circular mild steel plates of size 30 cm to 75 cm and thickness 25 mm with

chequered or grooved bottom.

(2) The size of the plate should be at least the 4 times the maximum size of soil particle present at

the test location. Lording arrangement such as gravity loading arrangement such as gravity

loading. Reaction loading or truss. For gravity loading, girders, sleepers and sand bags are

required.

(3) Remote control type hydraulic jack with pressure gauge of 10 to 30 tonnes capacity

(4) Proving ring of 10 to 30 tonnes capacity

(5) Four dial gauge of 25mm to 50mm range and 0.01 mm sensitivity, magnetic holder and

datum bars.

(6) Packing plates, loading column, spirit level and plumb.

PROCEDURE

(1) A pit square in plane of size equal to five times the width of plate is dug up to a depth less

than 0.3 m the depth of proposed foundation.

(2) The arrangements for obtaining reaction e.g. fixing of girders and anchors or truss or the dead

load are done.

(3) The pit is dug next to the full depth of foundation and a layer of fine sand not mare than 5 mm

is laid in the centre of pit .over this layer the plate is bedded properly.

(4) The loading frame, jack, proving ring etc. Are fixed keeping axially. Also the dial gauges on

all the four corners of plate are fixed with the help of magnetic holders fixed on datum bars

resting on immovable supports at a distance more than five times the width of plate.

(5) The loads are then applied with the help of the jack in equal increments of 250 kg in case of

soils with N




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(8) After completing the test, the assembly is taken out. The natural unit weight and moisture

content of soil in the pit is determined by in-situ tests or taking samples and testing those in

laboratory. The water table position should also be recorded.

APPLICATIONS

The data obtained from the test is utilised in evaluating the soil pressure for shallow foundations.

The is also used to determine the coefficient of modulus of sub grade reaction. The test is widely

used in soil exploration programme.

Determination of allowable soil pressure (non cohesive soils) - from the load intensity and

settlement plot, the bearing capacity of qu is obtained by drawing double tangents to the initial and

final portion of curve. This value of qu is utilised to obtain bearing capacity factor Nr as below:

Qu = 0.4r Bp Nr

Where, r =unit weight of soil; Bp = width of plate

Knowing Nr ,Nq is also obtain and thus for a particular footing, the bearing capacity from shear

calculation is calculated. By applying a suitable factor of safety, safe pressure is worked out.

Knowing the Sp the corresponding pressure intensity is read from the pressure settlement curve.

Out of the values obtained from the above two criteria, the least one is taken as allowable soil

pressure for an assumed size of footing.

The above method assumes that the soil strata are reasonably uniform upto the significant depth.

This should be verified by borings and samplings.

LIMITATIONS-

Plate load, though useful, only reflect the characteristic of soil located within a depth equal to

twice the width of plate. Since the foundations are generally generally larger, the settlement and

resistance against shear failure will depend on the properties of a much thicker stratum.

Also in case of layered soil, the results may be misleading. The method does not provide the

ultimate settlement particularly in case of cohesive soils. The results are affected with the

presence of water table. If the test is carried out when water table is deep but likely to rise

subsequently.

OBSERVATIONS AND CALCULATION

Size of pit = VPL/HPL Depth of pit = Date

Plate size = site No. Least count of dial gauge = PLACE

Proving ring No. =

S.

NO.

PR

DIV.

PRESSUR

E

DIAL

1

DIAL

2

DIAL 3 DIAL

4

AVERAGE

SETTLEMET




21

EXPERIMENT-06

UNCONFINED COMPRESSION TEST

Aim:- To determine the unconfined compressive strength of a cohesive soil.

Theory:- The unconfined compressive strength (qu) is the load per unit at which the cylindrical

specimen of a cohesive soil unconfined soil fails in compression.

qu = P/A

where P = axial load at the failure; A= corrected area = Ao /1-, where Ao initial area of the

specimen; = axial strain = change in length/original length.

The undrained shear strength(s) of the soil is equal to one half of the unconfined compressive

strength, s = qu/2.

Equipment:- 1) unconfined compression apparatus, proving ring type; 2) Proving ring, capacity

1kN, accuracy 1N; 3)Dial guage, accuracy 0.01mm; 4) Weighing balance ; 5) Oven; 6) Stop

watch; 7) Sampling tube; 8) Split mould, 38mm diameter, 76mm long; 9) Sample extractor; 10)

Vernier calipers; 11) Knife; 12) Large mould.

Procedure:-

1) Prepare the soil specimen at the desired water content and density in the large mould.

2) Push the sampling tube onto the large mould, and remove the sampling tube filled with the

soil. For Undisturbed samples, push the sampling tube into the clay sample.

3) Saturate the soil sample in the sampling tube by a suitable method.

4) Coat the split mould lightly with a thin layer of grease, Weigh the mold.

5) Extrude the sample out of the sampling tube into the split mould, using the sample

extractor and the knife.

6) Trim the two ends of the specimen in the split mould. Weigh the mould with the specimen.

7) Remove the specimen form the split mould by splitting the mould into two parts.

8) Measure the length and the diameter of the specimen with a vernier calipers.

9) Place the specimen on the bottom plate of the compression machine.

10) Adjust the dial guage and the proving-ring guage to the zero.

11) Apply the compression load to cause an axial strain at the rate of % to 2% per minute.

12) Record the dial guage reading, and the proving ring reading every thirty seconds upto a

strain of 6%. The reading may be taken after every seconds for a strain between 6% to 12%, and

every 2 minutes or so beyond 12%.

13) Continue the test until failure surfaces have clearly developed or until an axial strain of

20% is reached.

14) Measure the angle between the failure surface and the horizontal, if possible.

15) Take the sample from the failure zone of the specimen for the water content determination.




22

Data Sheet for Unconfined Compression Test

Initial length of the specimen,Lo = Initial diameter of the specimen,Do =

Initial area of the specimen,Ao = Initial volumeof the specimen,Vo =

Mass of the empty split mould = Mas of split mould + specimen =

Mass of the specimen,M = Bulk density, = M/Vo

Water content, w = Dry density, d =

Specific gravity of solids, G = Void ratio,e = Gw/ 1 =

S.No

.

Observation Calculations

Elapsed

time

Dial guage Proving ring Strain

= L/Lo

Corrected

area

A=Ao/(1-)

Compressive

stress()=P/A

Reading Deformation

(L)

Reading Load

(P)

Plot the curve between the compressive stress as ordinate and axial strain as abscissa.

Results:- From the plot, unconfined compressive strength, qu =

Shear strength, s = qu/2 =




23

EXPERIMENT-07

STANDARD PENETRATION TEST

OBJECT:-

To conduct standard penetration test and estimate the value of N.

APPARATUS:-

1) Equipment for making bore holes of 7.5 cm to 15 cm dia.

2) Standard penetration test sampler known as split spoon sampler.

3) A type drill rods with nipples (couplings) in 1m,1.5m and 2m lengths.

4) Drop weight of 65kg.

5) Driving head.

6) Guide rod, used to guide the fall of drop weight.

7) Lifting ball or hook used for extraction of rods and sampler.

8) Tripod hoist with manually operated winch and pulley,rope etc

9) Pipe wrenches and spanner set.

10) Casing pipe.

PROCEDURE:-

(1) Boring guide is fixed on a leveled ground by keeping the centre of boring guide on the

point of bore hole. The bore hole is made by a suitable method of boring. Bottom of the bore hole

is cleaned.

(2) The SPT sampler is cleaned properly by opening it before use. After cleaning, it is

assembled and connected with the drill rod. Over the drill rod, the driving head is fixed.

(3) This assembly is kept vertically at the centre of hole. The flaps of boring guide are closed

in order to keep the assembly in vertical direction.

(4) At the top of driving head which had threads, the guide rod is screwed. A mark, 75cm

above the driving head is made on the guide rod.

(5) The drop weight is attached to the rope of tripod hoist. By operating winch, this weight is

lifted.]

(6) The drop weight is brought over the guide rod keeping the guide rod in centre of the hole

of drop weight, it is lowered.

(7) From the top of lower flap of boring guide, marks made on drill rod at 15cm, 30cm, and

45cm.

(8) Next by using manually operated winch and rope the drop weight is operated. It is allowed

to fall from the height 75cm marked on the guide rod. The number of blows for each 15cm are

recorded.

(9) Initial 15cm is treated as seating and the number of blows for next 30cm are taken as N

value.

(10) After driving the sampler upto 45cm depth, the drop weight is taken out from the guide rod

and kept on the ground.




24

(11) The guide rod and driving head are next removed. Lifting bail is then fixed on the drill rod

and rope is tied to it. The drill rods are rotated with the help of pipe wrench in clockwise direction

and also the force is applied on the rope for pulling out the sampler and drill rods. The assembly

is then taken out.

(12) The sampler is removed from the drill rods and splitted to take the sample out. The sample

is collected in polythene bags for laboratory testing.

(13) The strata is identified during the boring from the soil coming out with the auger and also

the soil obtained from sampler is also identified. A record of these observations is kept.

(14) The SPT test in general is carried out at surface and then at an interval of 0.75 m or 1.5 m

or at the change of strata upto the required depth.

(15) After carrying out the test at one depth, the bore hole is extended further to next depth. The

test is again carried out by repeating process as described in steps (2) to (13). Also in other bore

holes the process is repeated for carrying out the test.

FACTORS AFFECTING N VALUE:-

The N values are affected by a number of factors e.g., characteristics of hammer, driving

rod, frequency of blows, size of bore hole, over burden pressure water table etc.However, the later

two are most important and the necessary corrections are to be applied on the observed N values

before using them for interpretation. Peak, Hanson, Thornburn (1974) suggested the following

correction due to over burden which has been incorporated in I.S code.

CN = 0.77 log10 20/p

Where, CN = correction factor

p = effective overburden pressure at the depth,>0.25kg/cm2

In case of fine coarse grained soils e.g. fine sands or silty sands below water table. If the

number of blows are more than 15, the following expression is used for finding out the corrected

value of N. Thus Nc = 15 + (N`- 15)

Where N` = N value obtained after applying the correction of overburden

Nc = Corrected value of N

APPLICATIONS:-

Terzaghi and peck (1948) suggested the correction between N, angle of internal friction

and relative density of the frictional soil.

TABLE : TERZAGHI CORRELATION OF N WITH AND Rd

N value 0-4 4-10 10-30 30-50 >50

Relative density

Rd(%)

0-15 15-35 35-65 65-85 >85

Angle of internal

friction

28.5 28.5-30 30-36 36-41 >41

Compactness Very

loose

Loose Medium Dense Very

dense




25

Terzaghi and Peck have also suggested a correlation between N- values and unconfined

compressive strength in clayey soils.

TABLE : CORRELATION OF N WITH qu

N Consistency Unconfined compressive strength qu in kg/cm2

2 Very Soft 0.25

2-4 Soft 0.25 0.50

4-7 Medium Soft 0.50 1

8-15 Stiff 1 2

15-30 Very Stiff 2 4

30 Hard 4 8

OBSERVATIONS:-

Location: Bore Hole No.

Depth (m) Penetration (cm) Number of Blows N - Value

0.75 0 15

15 30

30 45

1.5 0 15

15 30

30 45

2.25 0 15

15 30

30 45

For cohesionless soils, the values of N may be correlated to the values of Nr and Nq which

are used in determining the bearing capacity of soils. Such correlations are given by Peck,

Hanson, Thornburn (1974) in the form of curves.

Peck et al. (1974) gave the curves for finding out the soil pressure corresponding to 2.5 cm

settlement for known width of footing and correlated values of N in cohesion soils.




26

EXPERIMENT-08

DENSITY INDEX

OBJECT

To determine the density index.

SCOPE

This standard (part XIV) covers the laboratory method for the determination of the density Index (relative

density) of cohesion less free draining soils. Soils for which this method is Applicable may

contain upto 12 percent by weight of soil particles passing a 75 micron IS Sieve.

APPARATUS

(1) Vibratory Table-A steel table with cushioned steel vibrating deck about 75 x 75 cm. The vibrator

should have a net weight of over 45 kg. The vibrator shall have a frequency of 3600 vibration per

Minute, a vibrator amplitude variable between 0.05 and 0.65 mm under a 115 kg load and shall be

Suitable for use with a 220 v ac power source.

(2) Moulds- Cylindrical metal unit weight moulds of 3000 cm3 and 15000 cm

3 capacity conforming to

the dimensional requirements.

(3) Guide sleeves- one guide sleeve with clamp assembly for each size mould. Two of the three set

screws on the clamp assembly should be provide with lock nuts.

(4) Surcharge Base Plates with Handle- One surcharge base plate 10 mm in thickness for each size

mould.

(5) Surcharge weight- one surcharge weight for each size mould. The total weight of surcharge base

plate and surcharge weight shall be equivalent to 140 g/cm2 for the mould being used.

(6) Dial gauge holder

(7) Dial gauge -50 mm travel with 0.025 mm graduation calibration bar of metal and 75 x 300 x 3 mm

in size

(8) Pouring device consisting of funnels 12mm and 25mm in diameter and 15cm long , with cylindrical

spouts and lipped brims for attaching to 15 diameter and 30cm high metal cans.

(9) Mixing pans suitable size are 60 x 90 cm and 10 cm deep and 40 x 40 cm and 5 cm deep.

(10) Weighing scale portable platform scale ,100 kg capacity with sensitivity of 20 g in accordance with

IS : 1435-1960.

(11) Hoist suitable hoist of at least 135 kg capacity.

(12) Metal hand scoop.

(13) Bristled brush.

(14) Timing device including in minutes and seconds metal straight edge about 40 cm long.

(15) Micrometer - 0to 25 mm, accurate to 0.25 mm.




27

CALIBRATION

The volume of the mould should be determined by direct measured and checked by filling with

Water. The initial dial reading for computing the volume of the specimen should be determined.

(1) Determination of volume by Direct Measurement

The average inside diameter and height of the mould should be mould should be measured to 0.025 mm.

volume of the 3000 cm3 mould should be calculated to the nearest 3 cm

3 and that of 15000 cm

3. The

average inside cross sectional area of the mould should also be calculated in square centimetres.

(2) Determination of Volume by Filling with water

The mould should be filled with water and a glass plate should be slid carefully over the top surface of the

mould in such a manner as to ensure that the mould is completely filled with water. The temperature of the

water should be measured and the weight in grams of the water filling the mould should be determined.

The volume of the mould should be calculated in cubic centimetres by multiplying the weight of water by

the volume of water per gram at the measured temperature.

(3)Determination of initial Dial Reading for Computing the Volumes of the Specimen

The thickness of the surcharge base plate and the calibration bar should be measured to 0.025 mm using a

micrometer the calibration bar should then be placed across a diameter of the mould along the axis of the

guide brackets. The dial Gauge holder should be inserted in each of the guide bracket on the mould with

the dial gauge stem on the top of the calibration bar and on the axis of the guide brackets. The dial gauge

holder should be placed in the same position in the guide brackets each time by means of match marks on

the guide brackets and the holder. Six dial gauge reading should be obtained, three on the left side.




28

EXPERIMENT-09

Vane Shear Test

OBJECTIVE

To find shear strength of a given soil specimen.

NEED AND SCOPE

The structural strength of soil is basically a problem of shear strength.

Vane shear test is a useful method of measuring the shear strength of clay. It is a

cheaper and quicker method. The test can also be conducted in the laboratory. The

laboratory vane shear test for the measurement of shear strength of cohesive soils, is

useful for soils of low shear strength (less than 0.3 kg/cm2) for which triaxial or

unconfined tests can not be performed. The test gives the undrained strength of the soil.

The undisturbed and remoulded strength obtained are useful for evaluating the

sensitivity of soil.

PLANNING AND ORGANIZATION

EQUIPMENT

1.Vane shear apparatus.

2.Specimen.

3.Specimen container.

4.Callipers.

EXPERIMENTAL PROCEDURE

1.Prepare two or three specimens of the soil sample of dimensions of at least 37.5 mm

diameter and 75 mm length in specimen.(L/D ratio 2 or 3).

2.Mount the specimen container with the specimen on the base of the vane shear

apparatus. If the specimen container is closed at one end, it should be provided with a

hole of about 1 mm diameter at the bottom.

3.Gently lower the shear vanes into the specimen to their full length without disturbing

the soil specimen. The top of the vanes should be atleast 10 mm below the top of the

specimen. Note the readings of the angle of twist.

4.Rotate the vanes at an uniform rate say 0.1o/s by suitable operating the torque

application handle until the specimen fails.




29

5.Note the final reading of the angle of twist.

6.Find the value of blade height in cm.

7.Find the value of blade width in cm.

CALCULATIONS:

OBSERVATIONS:

Name of the project:

Soil description:

S.N

o

Initial

Readin

g

(Deg)

Final

Readin

g

(Deg.)

Differenc

e

(Deg.)

T=Spring

Constant/180

x Difference

Kg-cm

S=TxG

Kg/cm2

Averag

e 'S'

Kg/cm2

Spring

Consta

nt

Kg-cm

GENERAL REMARKS:

This test is useful when the soil is soft and its water content is nearer to liquid limit.




30

EXPERIMENT-10

UNDRAINED TRIAXIAL TEST

OBJECTIVE

To find the shear of the soil by Undrained Triaxial Test.

NEED AND SCOPE OF THE TEST

The standard consolidated undrained test is compression test, in which the soil specimen is first

consolidated under all round pressure in the triaxial cell before failure is brought about by increasing the

major principal stress.

It may be perform with or without measurement of pore pressure although for most applications the

measurement of pore pressure is desirable.

PLANNING AND ORGANIZATION

Knowledge of Equipment

A constant rate of strain compression machine of which the following is a brief description of one is in

common use.

a) A loading frame in which the load is applied by a yoke acting through an elastic dynamometer,

more commonly called a proving ring which used to measure the load. The frame is operated at a

constant rate by a geared screw jack. It is preferable for the machine to be motor driven, by a

small electric motor.

b) A hydraulic pressure apparatus including an air compressor and water reservoir in which air

under pressure acting on the water raises it to the required pressure, together with the necessary

control valves and pressure dials.

A triaxial cell to take 3.8 cm dia and 7.6 cm long samples, in which the sample

can be subjected to an all round hydrostatic pressure, together with a vertical

compression load acting through a piston. The vertical load from the piston acts on a




31

pressure cap. The cell is usually designed with a non-ferrous metal top and base

connected by tension rods and with walls formed of perspex.

Apparatus for preparation of the sample :

a) 3.8 cm (1.5 inch) internal diameter 12.5 cm (5 inches) long sample tubes.

b) Rubber ring.

c) An open ended cylindrical section former, 3.8 cm inside dia, fitted with a small rubber tube in its

side.

d) Stop clock.

e) Moisture content test apparatus.

f) A balance of 250 gm capacity and accurate to 0.01 gm.

Experimental Procedure

1. The sample is placed in the compression machine and a pressure plate is placed on the top. Care

must be taken to prevent any part of the machine or cell from jogging the sample while it is being

setup, for example, by knocking against this bottom of the loading piston. The probable strength of

the sample is estimated and a suitable proving ring selected and fitted to the machine.

2. The cell must be properly set up and uniformly clamped down to prevent leakage of pressure during

the test, making sure first that the sample is properly sealed with its end caps and rings (rubber) in

position and that the sealing rings for the cell are also correctly placed.

3. When the sample is setup water is admitted and the cell is fitted under water escapes from the

beed valve, at the top, which is closed. If the sample is to be tested at zero lateral pressure water is

not required.

4. The air pressure in the reservoir is then increased to raise the hydrostatic pressure in the required

amount. The pressure gauge must be watched during the test and any necessary adjustments must

be made to keep the pressure constant.

5. The handle wheel of the screw jack is rotated until the under side of the hemispherical seating of

the proving ring, through which the loading is applied, just touches the cell piston.




32

6. The piston is then removed down by handle until it is just in touch with the pressure plate on the

top of the sample, and the proving ring seating is again brought into contact for the begging of the

test.

Observation and Recording

The machine is set in motion (or if hand operated the hand wheel is turned at a constant rate) to give a

rate of strain 2% per minute. The strain dial gauge reading is then taken and the corresponding proving

ring reading is taken the corresponding proving ring chart. The load applied is known. The experiment is

stopped at the strain dial gauge reading for 15% length of the sample or 15% strain.

Operator : Sample No:

Date : Job :

Location : Size of specimen :

Length : Proving ring constant :

Diameter : 3.81 cm Initial area L:

Initial Volume : Strain dial least count (const) :

Cell

pressure

kg/cm2

1

Strain

dial 2

Proving ring

reading

3

Load on

sample kg

4

Corrected area cm2

5

Deviator stress

6

0.5

0

50

100

150

200

250

300

350




33

400

450

0.5

0

50

100

150

200

250

300

350

400

450

0.5

0

50

100

150

200

250

300

350

400

450




34

Sample No. Wet bulk

density gm/cc

Cell pressure

kg/cm2

Compressive

stress

at failure

Strain at

failure

Moisture

content

Shear

strength

(kg/cm2)

Angle of

shearing

resistance

1.

2.

3.

General Remarks

a) It is assumed that the volume of the sample remains constant and that the area of the sample

increases uniformly as the length decreases. The calculation of the stress is based on this new

area at failure, by direct calculation, using the proving ring constant and the new area of the

sample. By constructing a chart relating strain readings, from the proving ring, directly to the

corresponding stress.

b) The strain and corresponding stress is plotted with stress abscissa and curve is drawn. The

maximum compressive stress at failure and the corresponding strain and cell pressure are found

out.

c) The stress results of the series of triaxial tests at increasing cell pressure are plotted on a mohr

stress diagram. In this diagram a semicircle is plotted with normal stress as abscissa shear stress

as ordinate.

d) The condition of the failure of the sample is generally approximated to by a straight line drawn as a

tangent to the circles, the equation of which is = C + tan. The value of cohesion,C is read of the shear

stress axis, where it is cut by the tangent to the mohr circles, and the angle of shearing resistance () is

angle between the tangent and a line parallel to the shear stress.




35

EXPERIMENT-11

PROCTOR TEST

SCOPE

Compaction is the application of mechanical energy to a soil so as to rearrange its particles and reduce the void ratio. It is applied to improve the properties of an existing soil or in the process of placing fill such as in the construction of embankments, road bases, runways, earth dams, and reinforced earth walls. Compaction is also used to prepare a level surface during construction of buildings.There is usually no change in the water content and in the size of the individual soil particles.

The objectives of compaction are:

To increase soil shear strength and therefore its bearing capacity. To reduce subsequent settlement under working loads. To reduce soil permeability making it more difficult for water to flow through.

Laboratory Compaction The variation in compaction with water content and compactive effort is first determined in the laboratory. There are several tests with standard procedures such as:

Indian Standard Light Compaction Test (similar to Standard Proctor Test) Indian Standard Heavy Compaction Test (similar to Modified Proctor Test)

Indian Standard Light Compaction Test

Soil is compacted into a 1000 cm3 mould in 3 equal layers, each layer receiving 25 blows of a 2.6 kg or (2.5 kg) rammer dropped from a height of 310 mm above the soil. The compaction is repeated at various moisture contents.

Indian Standard Heavy Compaction Test

It was found that the Light Compaction Test (Standard Test) could not reproduce the densities measured in the field under heavier loading conditions, and this led to the development of the Heavy Compaction Test (Modified Test). The equipment and procedure are essentially the same as that used for the Standard Test except that the soil is compacted in 5 layers, each layer also receiving 25 blows. The same mould is also used. To provide the increased compactive effort, a heavier rammer of 4.9 kg (or 4.5 kg) and a greater drop height of 450 mm are used.




36

PROCEDURE

Take a representative oven-dried sample, approximately 5 kg in the given pan. Thoroughly mix

the sample with sufficient water to dampen it to approximately four to six percentage points

below optimum moisture content.

Weigh the proctor mould without base plate and collar. Fix the collar and base plate. Place the

soil in the Proctor mould and compact it in 3 layers giving 25 blows per layer with the 2.5 kg

rammer falling through.

Remove the collar, trim the compacted soil even with the top of the mould by means of the

straight edge and weigh.

Divide the weight of the compacted specimen by 944 cc and record the result as the wet

weight wet in grams per cubic centimeter of the compacted soil.

Remove the sample from the mould and slice vertically through and obtain a small sample for

moisture determination.

Thoroughly break up the remainder of the material until it will pass a no.4 sieve

as judged by the eye. Add water in sufficient amounts to increase the moisture

content of the soil sample by one or two percentage points and repeat the above

procedure for each increment of water added. Continue this series of

determination until there is either a decrease or no change in the wet unit weight

of the compacted soil.

CALCULATION

Wet density gm/cc =weight of compacted soil / 944.

Dry density = wet density/(1+w)

Where w is the moisture content of the soil.

Plot the dry density against moisture content and find out the maximum dry density and optimum

moisture for the soil.

OBSERVATIONS

Cylinder diameter cm.

height cm




37

weight of cylinder gm

volumn of cylinder cc

Density

Determination No.

Water to be added

(percent)

Weight of water to be

added (gm)

Weight of cylinder +

compacted soil

Weight of compacted soil

(gms)

Average moisture content

(percent)

Wet density

(gm /cc)

Dry density (gm/cc)

Water content

Container No.

Wt. Of container + wet soil

gms.

Wt. Of container + dry soil

gms

Wt of container alone gms.

Wt. Of water gm

Wt. Of dry soil gms.

Percentage of water

Content

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