Geotechnical Engineering II Experiments

Department : Civil EngineeringName of the Process: (Smooth and effective working of Civil

Engineering Department)

Doc. No: Ver. No;00

Issue No: 01 Date: 1 January 2010 Date: Page:1/40

Experiment No. 1

NAME OF EXPERIMENT – DIRECT SHEAR TEST1 AIM

To determine shear parameters ( c and φ ) of soil in under un-drained condition 2 APPARATUS

The shear box solid grid plates, base plates, loading pad, loading frame with slotted

weights (0.2kg/cm2, 0.5kg/cm2 1kg/cm2 and 1.5kg/cm2, proving ring of 100kg to 250kg

capacity, dial gauge 0.01 mm least count and stop clock. Loading frame 1000 kg capacity.

Balance 0.1gm mim. Capacity. Spatula and straight edge.

3 PREPARATION OF SPECIMANRemoulded SpecimensIn case of Cohesion less density moisture contents are given. Based on these values weigh

of dry soil is determined. The required moisture is added in the soil. The mould is

assembled with base plate at bottom followed by solid serration plate (perpendicular to

direction of shear force). The reference level is taken from the top of mould before samples

is poured. The soil is then tamped in the shear box itself in layers till the difference in the

layer shows 25 mm thickness of sample. The sample is then covered by solid serration

plate similar to bottom plate and finally a loading pad is placed.

4 THEORY:

This test is also called as ‘Box shear test’. The sample is subjected two dimensional

stresses such as normal stress in vertical direction and shear stress in horizontal direction

(at constant rate). The test is useful for freely drained material (sands) since pore water

pressure can not be measured. The main advantages of this test are that it is simple. The

disadvantage of the method is it can-not controlled the drainage conditions hence; it is not

suitable for fine grained soil. 5 PROCEDURE

Undrained Test – The shear box with the specimen, plain grid plate over the base plate at

the bottom of the specimen an ui7kd plain grid plate at the bottom top of the specimen is

fitted into position into load frame. The upper part of the shear box should be raised such

that a gap of about 1 mm is left between the two parts of the box.

The required normal stress (0.2kg/cm2, 0.5kg/cm2 1kg/cm2 in individual trial) is applied

and the rate of longitudinal displacement / shear stress application so adjusted (1.25

Prepared by Received by Approved by Issued by

Compiled copy if stamp is red colour

V.B. Deshmukh Geotechnical Engineering

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Dr. S.B. CharhateH.O.D.

Dr. S.D. Sawarkar Principal

Dr.H.S. ChoreM.R.



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mm/min) that no drainage is occurred in the sample during the test.

The test is now conducted by applying horizontal shear load to failure (indicated by

decrease in proving ring reading) or to 20 percent longitudinal displacement, whichever

occurs first.

The shear load readings indicated by the proving ring assembly and the corresponding

longitudinal displacements are noted at regular intervals (say 30 units). If necessary, At the

end of the test, the specimen is removed from the box and the final moisture content is

measured.

A minimum of three (preferably four) tests shall be made on separate specimens of the

same density.

6 CALCULATIONS

Shear strain is expressed as, 100×=L

δε , Where δ is shear displacement

Shear stress is given by, A

F=τ , where F is the maximum shear force calculated from

proving ring reading.

7 RESULTSThe shear parameters in the un-drained conditions are cohesion c =

Angle of internal friction, φ =

8 DISCUSSIONS

In case of sandy soil the c is close to zero and φ value is maximum. According to

Terzaghi φ < 28 0 is classified as loose sand whereas, 380>φ > 28 0 is medium dense

sand and φ >380 is very dense sand. For saturated clays φ = 0 0.

8 PRECAUTIONSSelect the proper capacity of proving ring. In any case PRR should not exceed maximum

values given in calibration chart.No vibrations should be transmitted to the sample during the test and there should not be

any loss of shear force due to friction between the loading frame and due shear box

container assembly.The normal stresses to be selected for the test should correspond to the field conditions

and design requirements.Prepared by Received by Approved by Issued by



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DATE OF SUBMISSIONGRADESIGNATURE




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OBSERVATIONS

DIRECT SHEAR TEST

Density, g/cc Date Moisture content Proving ring capacityDrainage condition Proving ring numberMax. Size of particle Proving ring factor C.F. Area of sample, A = 36 cm2 Dial Gauge constantLength of sample, L = 6 cmVolume, V = 90 cm3

DGR PRR Displacement mm

δ =DGR x constant

Shear strain %

100×=L

δε

Shear Force,

F= PRR x CF

Shear stress

A

F=τ kg/

cm2

0 03060Note: till PRR decreases or upto 20% strain whichever reaches earlier




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Experiment No. 2

NAME OF EXPERIMENT– DETERMINATION OF UNCONFINED

COMPRESSIVE STRENGTH1 AIM : To determine Undrained Cohesion of partly saturated clayey soil2 APPARATUS

a) Split mould- Diameter 38 mm and Height 76 mm

b) Seamless tubes -38 mm diameter and 50 mm height, 3 numbers.

c) Pressure cell with central pedestal (cell pressure opening is closed)

d) Proving ring (depending on stiffness of soil)

e) Dial gauge for deformation measurement 0.01mm per unit to max. 25 mm travel

f) Loading frame of 1t capacity, arrangement for application of different strain rate

g) Solid plates with loading pad

h) Vertical sampling ejector for transferring sample from UDS tube/ compaction mould

into seamless tube.

i) Horizontal ejector for transferring sample from seamless tube to mould.

j) Miscellaneous Equipment – Specimen trimming and carving tools, water content cans,

etc, spatula, vernier caliper. Balances –weighted to the nearest 0.01 g, whereas

specimens of 100 g or larger shall be weighed to the nearest 0.1 g.

k) Oven – thermostatically controlled, with interior of non-corroding material, capable of

maintaining the temperature at 110 + 50 C.

3. PREPARATION OF TEST SPECIMENThe soil specimen to be used for test may be undisturbed, compacted or remoulded.

3.1 Specimen size – The specimen for the test shall have a minimum diameter of 38 mm and

the largest particle contained within the test specimen shall be smaller than 1/8 of the

specimen diameter. If, after completion of test on undisturbed sample, it is found that

larger particles are present than permitted for the particular specimen size tested, it shall be

noted in the repot of test data under remarks. The height to diameter ratio shall be 2.

Measurements of height and diameter shall be made with Vernier calipers or any other

suitable measuring device to the nearest 0.1 mm.3.2 Undisturbed Specimens

The undisturbed is collected in UDS tubes from the site. The wax is removed and three

seamless tubes are penetrated with help of vertical extractor. The sample is then pushed




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into mould by horizontal extractor. The projected sample in the mould is then trimmed in order to make either surfaces of

sample perfectly perpendicular to axis of mould. The split mould is then opened and

sample removed by pushing solid plates on either sides of specimen.The mass and dimensions are measured and sample is assembled in the pressure cell.Representative sample cuttings shall be used for the determination of water content.

3.3 Remoulded Specimen The dry density and moisture content are given or obtained from proctor test to evaluate

dry mass of soil and moisture content. The known quantity of mixed soil sample is then

compacted into proctor mould statically or dynamically. The three seamless tubes are

pushed vertically in the mould by vertical extractor. The sample of size 38 mm diameter

and 76 mm height is obtained by pushing sample from seamless tube into mould in

horizontal extractor.

4. THEORY Unconfined compression test is a special tri-axial test. It is used when the soil to be tested

is a saturated clay and Φ = 00 condition prevails in the field. This test is similar to triaxial

compression test except cell pressure is zero. Hence, only one Mohr’s is required for

determination of ‘cu’. The figure shows Mohr’s circle and failure envelope.5. PROCEDURE

The specimen is placed on the central pedestal of cell. The top and bottom of the sample

covered with solid plate and loading pad on top solid plate. The cell cover is closed and

plunger is made in contact loading pad. The Dial (deformation) gauge and proving ring

(force measurement) are assembled on the loading frame. The deformation dial gauge and proving ring are adjusted to zero. Force shall be applied so

as to produce axial strain at a rate of 1/to 2 percent per minute. Force and deformation

readings are recorded at suitable intervals (usually 30 on dial gauge).The specimen is compressed until failure surfaces have definitely developed or the stress-

strain curve is well past or until an axial strain of 20 percent is reached.The failure pattern is sketched carefully and shown on the data sheet or on the sheet

presenting the stress-strain plot.The water content of the specimen is determined in accordance with geotechnical

engineering manual I using samples taken from the failure zone of the specimen.

6. CALCULATIONSStress-Strain values shall be calculated a follows:




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a) The axial strain, ε %, is determined is expressed as

1000

×∆=L

Lε

Where,

L = the change in the specimen length as read from the strain dial indicator, and

L0 = the initial length of the specimen.

b) The average cross-sectional area, A, at a particular strain shall be determined from the

following relationship:

0

1L

L

AA o

∆−=

Where,

A0 = the initial average cross-sectional area of the specimen

c) Compressive stress, σ c, shall be determined from the relationship

A

Pc =σ

Where,

P is the compressive force kg, and A = average cross-sectional area, cm2 Values of stress σ c, and strain, ε %, obtained from above calculations are plotted on

abscissa and ordinate respectively. The maximum stress from this plot gives the value of

the unconfined compressive strength, qu.

7. RESULTSThe unconfined compression strength qu

The un-drained cohesion cu

8 DISCUSSIONThe failure plane α is 450 if φ = 00 for fully saturated clay sample otherwise it is partly

saturated or particles oversize 2mm. 9 Proving ring reading and dial gauge reading are recorded within their limits as referred

from calibration chart.The selection of capacity of proving ring depends on stiffness of sample. The basic

physical properties also indicated the approximate strength.During the preparation and assembling of the sample a care must taken reduce the




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disturbances.DATE OF SUBMISSIONGRADESIGNATURE




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OBSERVATION TABLE

UNCONFINED COMPRESSION TEST

1. Details of the soil specimen:

i. Undisturbed or remoulded or compacted:

ii. Initial diameter, D0 mm

iii. Initial length, Lo mm

iv. Initial area, A0 cm2

v. Initial mass of the specimen g

vi. Initial density g/cm2

vii. Initial water content %

2. Proving Ring No.

3. Proving ring capacity

4. Proving ring factor, C

5. Dial Gauge Constant ,G

DGR PRR Compressive

Force in kg

PRR x CF

Deformation

ΔL = DGR x G

mm

Strain in

%

100ΔL/L0

Area A in

cm2

Compressive Stress

qu in kg/cm2

(1) (2) (3) (4) (5) (6) (7)03060

Note: Test is continued till PRR decreases or 20% whichever earlier




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Figure Schematic diagram showing sample in unconfined compression test




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Experiment No. 3

1 NAME OF EXPERIMENT – TRI-AXIAL COMPRESSION TEST2 AIM – Determination of the shear strength parameters of a partly saturated sample in

Unconsolidated Undrained Triaxial Compression without the measurement of pore water

Pressure. IS: is referred for the procedure.3 APPARATUS

Split Mould – 36 mm diameter and length 72 mm.Trimming knife – sharp-bladed, for example, a spatula or pallet knife.Metal StraightedgeMetal ScaleNon-Corrodible Plastic End-Caps – of the same material as the test specimen. The upper end

cap is to have a central spherical seating to receive the loading ram (see Note).Note: A solid plastic end cap, 20 mm thick, is normally satisfactory for use on soft or very soft soils.

Seamless tubes – in the form of a steel tube, open at both ends of internal diameter 36mm and

of length 50 mm.

The Rubber Membrane- the thickness should be selected having regard to the size, strength

and nature of the soil to be tested. A thickness of 0.2 to 0.3 mm is normally satisfactory.Membrane Stretcher – steel tube 38 mm diameter with rubber tube in the middle to for suction.Rubber Rings – of circular cross-section stretchable to suit the 36 mm diameter of the end

caps.Apparatus for Moisture content Determination – as described in Geotechnical engineering I

manual.Balance – readable and accurate to 0.1gVertical Extruders - to transfer sample from UDS tubes / compaction mould into seamless

tubes.Horizontal Extruder- It is a table mounted arrangement to push the sample from seamless tubes

into split mould.

Triaxial Test Cell – A transparent chamber to withstand the maximum pressure of 10 kg/cm2

and provided with a plunger for applying additional axial compressive load to the specimen by

means of a loading ram. is recommended. The base of the cell is provided with a suitable

central pedestal with drainage outlets with valves.Cylinder with pressure gauge for applying and maintaining the desired pressure on the Fluid

within the Cell – to an accuracy of 0.1 kg/cm2 with a gauge for measuring the pressure. The

cylinder is filled with 2/3 of volume by water.Loading frame - For Applying Axial Compression to the Specimen – 1 t loading capacity




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and operate at convenient speeds to convert the range 0.05 to .5 mm per minute. Proving ring- 100 kg capacity with sensitivity of 0.2 kg for low strength soils and one of 1000

kg capacity with sensitivity of 1 kg for high strength soils.

Dial Gauge – 0.01 mm least count with provision for maximum compression of 25 mm is

used.4. PREPARATION OF SPECIMENS4.1 Undisturbed Specimens

The object of specimen preparation is to produce cylindrical specimens of height twice the

specimen diameter with a plane ends normal to the axis and with the minimum change of the

soils structure and moisture content.

A specimen from a sampling tube of the same internal diameter as the required specimen may

be obtained as given in (a) to (e).

a) A UDS sample is cut from the site with and sealed with wax on either sides

b) The wax, used for sealing, is removed and the cutting edge end of the sample smoothed so

that it is approximately normal to the axis of the tube. Three seamless tubes are pushed

vertically into UDS tube which is held in vertical extruder. All seamless tubes are cut from

the UDS sample by rotating and lifting vertically.

c) The horizontal extruder is then used to push the each sample through the seamless tube

into split mould. The sample is leveled and then removed by opening split moulds.

d) The length, diameter and weight of the specimen is measured to an accuracy enabling the

bulk density to be calculated to an accuracy of + 1.0 percent.

e) The specimen is placed on one of the end caps and the other end cap is put on top of the

specimen. The rubber membrane shall then be placed around the specimen using the

membrane stretcher and the membrane sealed to the end caps by means of rubber rings.

f) The specimen is then ready to be placed on the pedestal in the Triaxial cell. The pedestal

covered with a solid end cap or the drainage valve is kept closed.4.2 Remoulded Samples

a) The dry weight of soil and quantity of water are calculated from the given density and

moisture. The soil mixed with moisture contained is then compacted in compaction mould by

dynamic or static method. The sample is then cut in three seamless tubes using vertical

extractor and finally pushed into mould by horizontal extractor. Follow the procedure in (c-f).5 THEORY




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Tri-axial test overcomes demerits of box shear test. It is more advantageous due measurement

of volume change during test and state of stress at any time during testing.Unconsolidated Undrained test is performed immediately the applying the confining pressure.

The failure loading is applied to the sample so rapidly that no pore water pressure can drain or

escape from the specimen during the test. The test will be always produce a value of φ of 00

for saturated cohesive soils, this is often describe as φ = 00 condition.

The choice of drainage condition depends on drainage condition expected in the site. If the soil

is sandy, excess pore pressure resulting from the new load usually expected to dissipete rapidly

and drained condition should be expected. If the soil is stressed in the field is saturated clay,

excess pore pressure dissipates slowly and φ = 00 condition governs: thus a UU test is the

proper choice.

The UU test is often called a ‘quick ‘test (Q test) because it can be performed quickly

compared to the other two types of loading and drainage tests. It is usually completed in 30

minutes per specimen. 6. TESTING PROCEDURE

The specimen prepared as described above is placed centrally on the solid circular plate in top

and bottom which is finally rest on the pedestal of the Triaxial cell. The cell is assembled with

the loading ram resting on solid plate and load pad.

The cell containing the specimen is placed in the loading machine. The operation fluid is

admitted to the cell from cylinder and the pressure is raised to the desired value.The proving ring and dial gauges are installed at their appropriate locations. The loading

machine is then further adjusted to bring the loading ram just in contact with the seat on the

top cap of the specimen and the initial reading of the gauge measuring the axial compression

of the specimen shall be recorded.

A rate of axial compression is selected (Gear No.1) such that failure is produced within a

period of approximately 5 to 15 minutes. The test commenced with a sufficient number of

simultaneous readings of the proving ring and dial gauge are taken to define the deviator

stress-axial strain curve.

The test is continued until the maximum value of the stress has been passed or until an axial

strain of 20 percent has been reached. Note: - It is often convenient to make a plot of load versus compression as the test proceeds, to




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enable the point of failure to be determined.The cell is drained of fluid, dismantled and the specimen taken out. The rubber membrane is

removed from the specimen and the mode of failure shall be noted (see Note 1).

The specimen is weighed (see Note 2) and samples for the determination of the moisture

content of the specimen is taken [see Geotechnical Engineering Manual I]. If there is a

moisture change in the specimen, it should be recorded and discretion used with regard to

acceptability of the test.

Note 1: - The most convenient method of recording the mode of failure is by means of a sketch

indicating the position of the failure planes. The angle of the failure plane (s) to the horizontal

may be recorded, if required. These records should be completed without undue delay to avoid

loss of moisture from the specimen.Minimum three samples are tested at higher cell pressure (usually twice the earlier pressure).Note 2 – Comparison with the recorded weight of the specimen before testing provides a check

on the impermeability of the rubber membrane if water has been used as the operating fluid in

the cell.

7. CALCULATIONSStress-Strain values shall be calculated a follows:

d) The axial strain, ε %, is determined is expressed as

1000

×∆=L

Lε

Where,

L = the change in the specimen length as read from the strain dial indicator, and

L0 = the initial length of the specimen.

e) The average cross-sectional area, A, at a particular strain shall be determined from the

following relationship:

0

1L

L

AA o

∆−=

Where,

A0 = the initial average cross-sectional area of the specimen

f) Deviator stress, σ d, is determined from the relationship




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A

Wdd =σ

Where,

Wd is the compressive force kg, and A = average cross-sectional area, cm2

g) The major principal stress is expressed as, σ 1 =σ d +σ 3 where, σ 3 is minor cell pressure.8. RESULTS

The undrained cohesion cu =

Angle of Internal Friction φ = 9 PRECAUTION

Proving ring reading and dial gauge reading are recorded within their limits as referred from

calibration chart.The elastic membrane must dry and dusted in power in order to reduce the friction.The selection of capacity of proving ring) depends on stiffness of sample. The basic physical

properties also indicated the approximate strength.During the preparation and assembling of the sample a care must taken reduce the

disturbances.DATE OF SUBMISSIONGRADESIGNAURE




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OBSERVATIONS

TRIAXIAL COMPRESSION TEST

Specimen preparation procedure Bulk Density,g/cm3

Initial length of specimen, L NMC

Initial diameter of sample, d

Initial Area of sample, Ao Rate of strain

Initial weight of specimen Dial gauge least count ‘C’

Proving ring No. Sketch of specimen after failure

Proving ring capacity

Mode of failure

Angle of failure plane with vertical

Cell pressure σ3 = .. kg/ cm2

Dial

gauge

Reading

(DGR)

Proving

Ring

Reading

(PRR)

δl = DGR x

C

Strain %

100×=L

lδε

Deviator

Load

Wd =

PRR*CF

Corrected Area

1001

0 ×−

=

L

l

AA f δ

Deviator

Stress,

kg/cm2

fd A

Wdσ

Note: CF = Refer calibration chart

From the stress-strain curves principle stresses are evaluated as

Sample No. 1 2 3Maximum deviator stress, σ dmax kg/cm2

Cell pressure σ 3, kg/cm2

Major principal stress, σ 1,= σ 3,+ σ dmax

kg/cm2




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Experiment No 4

NAME OF EXPERIMENT –CONSOLIDATION TEST1 AIM

To determine the compressibility parameters i.e. coefficient of consolidation (cv) , coefficient

of compressibility (av) , compression index (cc) , coefficient of volume change (mv) and

preconsolidation pressure (pc).2. APPARATUS2.1 Consolidating Ring

The diameter of ring 60 mm and 20 mm thick. The ring is rigid and made of a material

which is non-corrosive. The inner surface is smooth and highly polished.The ring shall be provided with a cutting edge in order to facilitate preparation of specimens.The height of the ring shall not be less than 20mm with a diameter to height ratio of about

3.0 and further the specimen height shall be not less than 10 times the maximum particle

size.2.2 Porous Stones

These stones are placed at the top and bottom of the soil specimen, and shall be of silicon

carbide, aluminum oxide or other porous materials not attacked by the soil. The porosity of

the stones are such that free drainage is assured throughout the test, but that no intrusion of

soil into the pores of the stones takes place.

A sheet of Whatman No. 54 filter paper of diameter equal to that of the stone, may be placed

between the stone and the soil surface in order to prevent intrusion.2.3 Consolidation Cell – A container within which is placed the consolidation ring containing

the specimen between the top and bottom porous stones. The cell is capable of being filled

with water to a level higher an axial vertical load applied to the top of the specimen and of

allowing measurement of the change in height of the specimen on its central axis.2.4 Dial Gauge – The gauge that read to an accuracy of at least 0.01 percent of the specimen

height and have a travel of at least 50 percent of the specimen height. 2.5 Loading Device

A device which enables vertical force to be applied axially in suitable increments, to the test

specimen, through a suitable loading yoke. The force is applied to the loading cap of the specimen centrally through some form of

spherical seating. The applied load is known to an accuracy of at least + 1percent. The loading device permits application of a load increment within a period of 2 s without




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significant impact.Trimming Equipment – Metal straightedge, thin bladed trimming knife (like spatula).Equipment for Measuring Initial Height of Test Specimen to Accuracy of 0.1 mm – Vernier

reading calipers.Moisture Content Containers and Drying Air-Oven Maintained at 110 + 50C, Desiccator.Balance Sensitive to 0.01 g – For weighing the specimen and moisture content.Stop watch readable to 1 s.

3. THEORY

Every structure resting on soil settles therefore, compressibility is the important physical

property. It is the dependent properties. Compressibility of soil is related to magnitude of

settlement and time of settlement. The experimental determination is based on one

dimensional consolidation that takes place along vertical direction of saturated compressible

soil. The coefficient compressibility Cv indicates the time required for settlement of

foundation. The compression index Cc, coefficient of volume change mv, determines the

magnitude of settlement. The types of clay deposits depends on the magnitude of

preconsolidation pressure pc whereas 1-Dimensional consolidation is is similar to

permeability hence, an approximate value of coefficient of permeability is also determined.

The Darcy’s law is valid and sample is fully saturated before it is consolidated. This test

consolidates the undisturbed soil but can be extended to compacted soil.

4.

4.1

PROCEDURE

Preparation of Test Specimen Determine the weigh the empty consolidation ring (W1).If the specimen is prepared from a UDS sample, a representative sample for testing is

extruded and cut off, care is taken to ensure that the two plane faces of the resulting soil disc

are parallel to each other. The thickness of the disc of soil shall be somewhat greater than the

height of the consolidation ring.The consolidation ring with cutting edge is gradually inserted into the sample by pressing

with hands and carefully removing the material and the ring. The consolidation ring is

sometimes pushes along with a guide ring placed on the top. The surrounding of sample is

loosened by spatula and entire assembly is cut at bottom. The soil sample thus obtained is trimmed flush with the top and bottom edges of the ring.

For soft to medium soils, excess soil should be removed using a wire saw and final trimming




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may be done with a straight edge, if necessary. For stiff soils, a straight edge alone is used

for trimming. Excessive remoulding of the soil surface by the straight edge should be

avoided. In the case of very soft soils, special care should be taken so that the specimen may

not fall out of, or slide inside the ring during trimming.A sample of soil similar to that in the ring. Taken from the trimming, is used for determining

moisture content.The thickness of the specimen (H0) shall be measured and weighed immediately (W2).

4.2 Assembly of ApparatusThe bottom porous stone are centered on the base of the consolidation cell When testing

softer, normally consolidated clays, the porous stones are made wet and covered by a wet

filter paperThe ring and specimen are placed centrally on the bottom porous stone and the upper porous

stone, and then the loading cap are placed on top. A small water chamber with head of water

equaled to mid height of sample is connected at the bottom of consolidometer. In new type

of consolidometer spce between the cell and outside boundary is filled with water.The consolidometer is placed in position in the loading device and suitably adjusted. The dial

gauge is then clamped into position for recording the relative movement between the base of

the consolidation cell and the loading cap. A seating pressure of 0.05 kgf/cm2 is applied to

the specimen.The specimen shall then be allowed to reach equilibrium for 24 h.

4.3 LoadingFor consolidation testing, it is generally desirable that the applied pressure at any loading

stage be double than at the preceding stage. The test may therefore be continued using a

loading sequence which would successively apply stress of 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 and 6.4

kgf/cm2, etc, on the soil specimen.For each loading increment, after application of load, readings of the dial gauge are taken

using a time sequence such a 0, 0.25, 1, 2.25, 4, 6.25, 9, 12.25, 16, 20.25, 25, 36, 49, 64, 81,

100, 121, 144, 169, 196, 225, min, etc, up to 24 h or 0, ¼, ½, 1, 2, 4, 8, 15, 30 and 60 min,

and 2,4,8 and 24 h. These time sequences facilitate plotting of thickness or change of

thickness of specimen against square root of time or against log time.

The loading increment is left at least until the slope of the characteristic linear secondary

compression portion of the thickness versus log time plot is apparent, or until the end of

primary consolidation is indicated on a square root of time plot. A period of 24 h will usually Prepared by Received by Approved by Issued by



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be sufficient, but longer times may be required. If 24 h are seen to be sufficient, it is

recommended that this commonly used load period be used for all load increments. In every

case, the same load increment duration is used for all load increments during a consolidation

test.It is desirable that the final pressure be of the order of at least four times the pre-

consolidation pressure, and be greater than the maximum effective vertical pressure which

will occur in-situ due to overburden and the proposed construction.On completion of the final loading stage, the specimen is unloaded by pressure decrements

which decrease the load to ¼ of the last load. Dial gauge readings are taken as necessary to

proceed much more rapidly (after every 2 hours.)On completion of this decrement, the water shall be siphoned out of the cell and the

consolidometer is quickly dismantled after release of the final load. The specimen,

preferably within the ring, is wiped free of water, weighed (W3) and thereafter placed in the

oven for drying. If the ring is required for further testing, the specimen may be carefully

removed from the ring in order to prevent loss of soil, and then weighed and dried.Following drying, the specimen with ring is reweighed (W4).The specific gravity of the sample is determined at the end.

5. CALCULATIONS5.1 Coefficient of consolidation, cv

The coefficient of consolidation, cv, for the load increment under consideration may be

calculated from the formula:

( )90

2848.0

t

HC av

v =

Where,

Hav is the average specimen thickness for the load increment




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5.2

5.3

Relation between void ratio e and effective σ pressure

Methods

i) Change in void ratio method and

ii) Equivalent height of solid method

In change in void ratio method

Change in height after every increment of effective pressure H is given as

HHH ∆−= 0

Whereas, ΔH mm= (Final DGR-Initial DGR) and Ho is the original height of sample

Final void ratio, ef is given by

Gwe ff =

Where, wf is the final moisture content at the end of consolidation

Change in void ratio Δe is given as

( )H

H

ee

f

f ∆+

=∆1

The coefficient of compressibility, av

From the plot of the void ratio, e versus σ , the slope of the straight line portion that is for

the soil in the normally consolidated state is designated as Coefficient of compressibility, av

cm2/kg is given by

σ∆∆= e

av

5.4 Compression Index, Cc

From the plot of the void ratio, e versus log σ . The slope of the straight line portion that is

for the soil in the normally consolidated state is designated as Cc. This can be directly

obtained from the plot or calculated as:

∆=

1

2logσσe

Cc

5.5 Coefficient of volume change




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σ∆+= e

mv

1

5.6 Coefficient of Permeability K

wvv mck γ=5.7 Coefficient of Permeability K

wvv mck γ=

6. RESULTS Applied pressurecoefficient of consolidation, cv

coefficient of compressibility av

compression index cc

coefficient of volume change mv

preconsolidation pressure pc

Approx. coefficient of permeability, k

Initial void ratio, e7 DISCUSSIONS

The pressure increment (effective stress) depends on actual effective overburden stress at

site. The increment varies from 60% to 200% of that effective overburden pressure. In case

of stiff clay pressure increment may be may starts from 0.2 kg/cm2 to 8 kg/cm2 but in no case

it exceeds ultimate bearing capacity.8 PRECAUTIONS

The porous stones used for drainage should be saturated for 48 hrs and boiled for at least half

an hour before used in the test.

The use of oil is strictly not recommended during the cutting and leveling of the sample.

The sample preparation is skilled process at least disturbances are allowed during the

preparation.

The spatula used in cutting / leveling the sample must be wet each time before touch to the

sample.

The set up should be free from any shocks, vibrations and direct access to outsiders.DATE OF SUBMISSIONGRADESIGNAURE




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s a m p le

D ia l G a u g e

P o r o u s S t o n e s

S a tu r a t i o n t a n k

Figure : Cross-section of Odometer




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OBSERVATIONS

CONSOLIDATION TEST

Project ………………………………… Specimen measurements Water contentSample No. …………………………… Diameter D =……………… cm Can no. = …………………………Soil Identification ………………………. Area A = π D2/4 ………….. cm2 Wt. of can + wet soil = ………… gSpecific gravity …………………………. Thickness H0 = ……………. Cm Wt. of can + dry soil = ………… gSpecimen preparation ………………… Wt. of ring (W1) = …………… g Wt. of can = …………………….g Procedure ……………………………… Wt. of specimen + ring (W2) = …….. g Wt. of water = …………............. gType of water used …………………… Final wt. of specimen (W3) = ………. Wt. of dry soil = ……………….. g

Dry wt. of specimen + ring (W4) …….. g Water content, percent = …………Density = ……….. g/cm3

Consolidation test: pressure increment data

Date Time

elapsed,

min

Dial Gauge Reading DGR Remarks

Loading Unloading0.1kg/

cm2

0.2

kg/cm2

0.4

kg/cm2

0.8

kg/cm2

1.6

kg/cm2

3.2

kg/cm2

6.4

kg/cm2

6.4kg/cm2 Unloading

readingsAre

1.6kg/cm2 recordedevery two

0.4kg/cm2 hrs

0.1kg/cm2




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Relation between void ratio e and effective σ pressure

Hf = Gwe ff = ( )

HH

ee

f

f ∆+

=∆1

Applied

Pressure

(kgf/cm2)

σ

Final Dial

Reading

Compression

H (mm)= Diff.

in successive final

DGR

Specimen height

H (cm)= H0 -H

e Void

Ratio

e

Remarks

(1) (2) (3) (4) (5) (6) (7)

Last reading Hf =




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Experiment No 5

NAME OF EXPERIMENT : VANE SHEAR TESTS1 AIM

To determine shear strength of saturated clay with referenced to IS 2720 Part (30)1980

2. APPARATUS2.1 Vane – The vane consist of four blades each fixed at 900 to the adjacent blades as

illustrated. It should not deform under the maximum torque for which it is designed. The

penetrating edges of vane blades are sharpened having an included angle of 900. The vane

blades are welded together suitably to a central rod, the maximum diameter of which

should preferably not exceed 2.5 mm in the portion of the rod which goes into the specimen

during the test. The vane is properly treated to prevent rusting and corrosion.

2.2 The frame: The apparatus maybe either of the hand-operated type or motorized. Provisions

should be made in the apparatus for the following:

a) Fixing of vane and shaft to the apparatus in such a way that the vane can be lowered

gradually and vertically into the soil specimen.

b) Fixing the tube containing the soil specimen to the base of the equipment for which it

should have suitable hole.

c) Arrangement for lowering the vane into the soil specimen (contained in the mould fixed

to the base) gradually and vertically, and for holding the vane properly and securely in

the lowered position.

d) Arrangement for rotating the vane steadily at a rate of approximately 1/60 rev/min

(0.10/s) and for measuring the rotation of the vane.

e) A torque applicator to rotate the vane in the soil and a device for measuring the torque

applied to an accuracy of 0.05 cm. kgf.A typical form of the hand/motorized apparatus is shown in Figure.

Graduated circle calibrated 0-3600

Mould : Diameter 30 mm and Height 70 mm

Spring: Stiffness varying from 2kg/cm2 to 8kg/cm2

3. THEORY




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Laboratory vane shear test is used for soft saturated clayey (cu= 12.5 kN/m2) soil which is

difficult to withstand the self weight. This is kind of test where failure of sample is due

to torque application.

4. PROCEDURE

The specimen in the tube should be at least 30 mm in diameter and 75 mm long. If the

specimen container is closed at one end, it should be provided at the bottom with a hole of

about 1 mm diameter. Cut the undisturbed specimen and find out the density and small

sample for NMC.

Mount the specimen container with specimen on the base of the vane shear apparatus and

fix it securely to the base. Lower the shear vanes into the specimen to their full length

gradually with minimum disturbance of the soil specimen so that the top of the vane is at

least 10 mm below the top of specimen. Note the readings of the strain and torque

indicators. Rotate the vane at a uniform rate approximately 0.10/s by suitably operating the

torque applicator handle until the specimen fails. Note the final reading of the torque

indicator. Torque readings and the corresponding strain reading may also be noted at

desired intervals of time as the test proceeds.Just after the determination of the maximum torque, rotate the vane rapidly through a

minimum of ten revolutions. The remoulded strength is then be determined within 1 minute

after completion of the revolution.

5. CALCULATIONS

Un-drained shear strength kg/cm2

+

=

622 dH

d

TS u

π

Where,

T is the torque kg-cm

d is the diameter of vane in cm

H is the height of vane in cm




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Sensitivity ( )( ) remouldedS

dundistrubeS

u

u=

6

7

8

RESULTS

The undrained shear strength of clay is evaluated as

Sensitivity

DISCUSSIONS

The cu determined from above results shows …..clay. The sensitivity for marine clay

obtained from Thane creek shows 5-12.

PRECAUTIONS

It is important that the dimensions of the vane are checked periodically to ensure that the

vane is not distorted or worn out.

DATE OF SUBMISSION

GRADE

SIGNAURE




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Figure : Typical hand/motorized vane shear apparatus




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Figure: Details of vanes attached to vane rod




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OBSERVATIONS

VANE SHEAR TEST

Bulk Density, kg/cm2

NMC

Diameter of Vane, D

Height of Vane, H

Spring Factor, K kg-cm

A) Undisturbed Shear Strength

Sr. No. Initial Reading

degree

Final

Reading

degree

Difference

in radians

Torque T

=Difference x K

Shear

Strength Su

kg/cm2

12 Average undisturbed shear strength Su kg/cm2

B) Remoulded Shear Strength

Sr. No. Initial Reading

degree

Final

Reading

degree

Difference

in radians

Torque T

=Difference x K

Shear

Strength Su

kg/cm2

12 Average disturbed shear strength Su kg/cm2




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Experiment No. 6

NAME OF EXPERIMENT- CALIFORNIA BEARING RATIO TEST

1 AIM

Laboratory determination of California Bearing Ratio at un-soaked condition.

2 APPARATUSMoulds with Base Plate: 150 mm diameter and 175 mm in height and base plate of 235

mm diameter.

Stay Rod and Wing Nut - Spacer Disc, Metal Rammer, WeightsLoading Machine - With a capacity of at least 5 000 kg and equipped with a movable

head or base which enables the plunger to penetrate into the specimen at a deformation

rate of 1.25 mm/min- The machine is equipped with a load device that can read to

suitable accuracy.Penetration Plunger: 50 mm diameter and height of 50 mm with hole for connectionDial Gauges - Two dial gauges reading to 0.01 mm least countSieves – 4.75 mm and 19 mm IS sievesMiscellaneous Apparatus - Other general apparatus, such as a mixing bowl, straightedge,

scales, soaking tank or pan, drying oven, filter paper, dishes and calibrated measuring jar.Surcharge weights – 2.5 kg annular weights of two numbers

3 PREPARATION OF SPECIMEN

The dry density for a remoulding is either the field density or the value of the maximum

dry density estimated by the compaction tests or any other density at which the bearing

ratio is desired.

The water content used for compaction is the optimum water content or the field

moisture as the case may be.

Soil Sample - The material used in the remoulded specimen passes a 19-mm IS Sieve.

Allowance for larger material is made by replacing it by an equal amount of material

which passes a 19-mm IS sieve but is retained on 4’75-mm IS Sieve.

Statically Compacted Specimens - The mass of the wet soil at the required moisture

content to give the desired density when occupying the standard specimen volume in the

mould shall be calculated. A batch of soil shall be thoroughly mixed with water to gives

the required water content. The correct mass of the moist soils is placed in the mould and




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compaction obtained by pressing in the displacer disc, a filter paper being placed

between the disc and the soil.

Dynamically Compacted Specimen - For dynamic compaction, a representative sample

of the soil weighing approximately 4.5 kg or more for fine-grained soils and 5.5 kg or

more for granular soils is taken and mixed thoroughly with water. If the soil is

compacted to the maximum dry density at the optimum water content the exacta mass of

soil required is taken and the necessary quantity of water added so that the water content

of the soil sample is equal to the determined optimum water content. The mould with the

extension collar attached shall be clamped to the base plate. The spacer disc shall be

inserted over the base plate and a disc of coarse filter paper placed on the top of the

spacer disc. The soil-water mixture shall be compacted into the mould.

The extension collar is then removed and the compacted soil carefully trimmed even with

the top of the mould by means of a straightedge. Any hole that may then, develop on the

surface of the compacted soil by the removal of coarse material, is patched with smaller

size material; the perforated base plate and the spacer disc are removed, and the mass of

the mould and the compacted soil specimen recorded. A disc of coarse filter paper shall

be placed on the perforated base plate, the mould and the compacted soil is inverted and

the perforated base plate clamped to the mould with the compacted soil in contact with

the filter paper.

4 THEORY

The potential soil subgrade is assessed by CBR method. It is used for design of thickness

of pavement. Lower the CBR value indicates poor subgrade and hence, higher the

thickness required. The CBR value of a soil is considered to be an index which in some

fashion is related to its strength. The value is highly dependent on the condition of the

material at the time of testing. Recently, attempts have been made to correlate CBR

values to parameters like modulus of subgrade reaction, modulus of resilience and

plasticity index, with considerable success.

The load settlement curve (standard curve) for perfectly contacted plunger and error

curve (modified curve) are shown in following figure.




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The standard load at various penetration are given as

Penetration mm Standard load, kg Standard pressure kg/cm2

2.5 1370 705 2055 105

5 PROCEDURE

Penetration Test (see Figure) - The mould containing the specimen, with the base plate in

position but the top face exposed, is placed on the lower plate of the testing machine.

Surcharge weights, sufficient to produce an intensity of loading equal to the weight of




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the base material and pavement are placed on the specimen.

The plunger is seated under a load of 4 kg so that full contact is established between the

surface of the specimen and the plunger.

The load and deformation gauges are then be set to zero. Load is applied to the plunger

into the soil at the rate of 1.25 mm per minute. Reading of the load are taken at

penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 4.0, 5.0, 7.5, 10.0 and 12.5 mm (The maximum

load and penetration is recorded if it occurs for a penetration of less than 12.5 mm). The

plunger shall be raised and the mould detached from the loading equipment. About 20 to

50 g of soil shall be collected from the top 30 mm layer of the specimen and the water

content determined.

The penetration test may be repeated as a check test for the rear end of the sample.

6 CALCULATIONS

California Bearing Ratio - The CBR values are usually calculated for penetrations of

2.5 and 5 mm. Corresponding to the penetration value at which the CBR values is

desired, corrected load value are taken from the load penetration curve and the CBR

calculated as follows:

100... ×=s

T

P

PRBC

PT =corrected unit ( or total ) test load corresponding to the chosen penetration from the

load penetration curve, and

PS =unit (or total) standard load for the same depth of penetration as for Pr taken from

the table presented above.

7 RESULTS

The CBR at 2.5 mm penetration

The CBR at 5 mm penetration

Design CBR8 DISCUSSIONS

Generally, the CBR value at 2’5 mm penetration will be greater than that at 5 mm

penetration and in such a case, the former shall be taken as the CBR value for design

purposes. If the CBR value corresponding to a penetration of 5 mm exceeds that for 2.5 Prepared by Received by Approved by Issued by



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mm, the test shall be repeated. If identical results follow, the CBR corresponding to 5

mm penetration shall be taken for design.9 PRECAUTIONS

The contact between plunger and soil must be 100% with plunger moves perfectly

vertical in order to avoid the error in load application.

The proving ring selected generally higher capacity for dense soil. DATE OF SUBMISSIONGRADESIGNAURE

10 OBSERVATIONS

CBR TEST

Density

NMC

Condition of specimen at undisturbed/remoulded/

Test : soaked/unsoaked

Type of compaction : Static/Dynamic Compaction

Light/Heavy Compaction

Proving ring capacity

Proving ring No.

Proving ring load factor ‘C’

Dial Gauge Constant

Surcharge weight usedPenetration Data

DGR PRR Penetration mm =DGR x G Load kg= PRR x C




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Figure: Set up for CBR test




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Geotechnical Engineering II Experiments

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