soil lab guru

8/13/2019 Soil Lab Guru

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1

DENSITY INDEX

Aim :

To determine density index of the given soil.

Apparatus :

Empty mould pouring device, IS 2720 Part IV 3600 RPM

Vibrating machine, scale, Vernier Calipers.

Reference Procedure :

Is 2720 (Part 14)- 1983

1) The diameter, height and weight of the empty mould weremeasured and noted down.

2) The mould was then filled completely with given soil sampleand weight of the mould with soil was taken down.

3) The mould filled with soil was placed on the vibrator andallowed to vibrate for about 4 minutes and it is said to be

forward vibration.

4) The vibration was done carefully and after switching it off,the sand left on the pan of the vibrator machine was

collected and poured into the mould.

5) Then again reverse vibration was done for 4 minutes and thescrews were opened.

6) The height of the sand in mould is reduced due to vibrations,was measured and volume of reduced sand was calculated.

7) The density of soil in both loose state and compacted stateswere determined.

OBSERVATIONS:

Height of mould, h1=

Diameter of mould, d =

Volume of mould, V1=2

4d h

Weight of the mould W1=

Weight of the mould + sand after pouring into mould, W 2 =

Weight of sand + mould after vibrating , W3=

Height of compacted soil after vibrating h2= h1(reduction in

height) =

H2=

Volume of compacted soil, V2=2

24

d h

Assume insitu dry density of soil

rd= 160g/cc

CALCULATIONS:

rdmax= w3-w1g/cc


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2

rdmin=2 1

1

w w

v

g/cc

Density Index (ID) or Relative Density (RD) :

Density index is an important index property of the soil, particularly

coarse grained material. It is expressed as :

ID=max

max min

e e

e e

- (1)

Emax : Void ratio of the soil in compacted condition .

E : Void ratio of the soil in normal condition.

Emin : Void ratio of the soil in loose condition .

It can also be expressed as :

ID= max min

max min

d d d

d d rd

r r r

r r

X 100 - (2)

As e=Grw/rd-1

RESULT:

Density Index of given soil =

GENERAL REMARKS:

INFERENCE :

As density index of given soil is 44.44%, the sand is of medium

dense type soil.

1) The Engineering properties of a mass of cohesionless soildepend to a large extent on its relative density (Dr) or density

index (ID).

2) The relative density of a soil gives a more clear idea of thedenseness than does the void ratio.

3) Two sands possessing the same relative density value,usually behave in identical manner.

PRACTICAL SIGNIFICANCE :

1)The relative density of a soil indicates how it would

behave under loads.

2) If the deposit is dense, it can take heavy loads with very

little settlements.

PRACTICAL VALUES:

Depending upon the relative density, the soils are generally divided

into 5 categories:

Denseness Very

Loose

Loose Medium

Dense

Dense Very

Dense

Dr (%)


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3

DETERMINATION OF COEFFICIENT OF

PERMEABILITY BY FALLING HEAD METHOD

AIM:

To determine the coefficient of permeability of given soil by falling

head method.

APPARATUS :

Permeameter with accessories, beaker, measuring jar and stopwatch.

REFERENCE:

IS : 2720 (Part 17)1986.

THEORY:

The variable head permeameter is used to measure the permeabilityof relatively less pervious soils.

The Coefficient of permeability is given by

K = 1102

2.30log

aL h

At h

Where

h1= Initial reading, cm = Initial head

h2= Final reading, cm = Final head

t = Time interval, sec

a = Cross- sectional area of the stand pipe, cm2

A = CrossSectional area of the specimen.

L = Length of the specimen

PROCEDURE:

1) The dimensions of the mould i.e. diameter and length of themould was measured.

2) The volume of the mould was calculated and from known

values of water content, dry density, Volume and wet weight

of the soil was completed.

3) About 2 kg of thoroughly mixed wet soil sample was taken

and wet weight of the soil completed was filled into the

mould, after applying grease to the inside

Surface of the mould. The soil was compacted at the required

dry density using a suitable compacting device.

4) The porous discs were saturated.

5) A porous disc was placed on the drainage basin and a fitter

paper was kept on the porous disc.

6) The dummy plate was removed, the mould with soil was

placed on the drainage base, after inserting a washer in

between.

7) The porous disc and the drainage cap were fixed using

washers.

8) The water reversion was connected to the outlet of the base,

and the water was allowed to flow upwards till it has

saturated the sample. Then the reservoir was disconnected

from the outlet at the bottom.


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9) The constant head reservoir was connected to the drainage

cap inlet.

10)The stop cork was opened and the water was allowed to

flow downward so that all the air was removed.

11)The stop cork was closed and the water was allowed to flow

through the soil such that steady state was attained.

12)The water flowing out of the base was collected in a flask for

time interval of measured by stop watch.

13)Repeated the procedure for same quantity of water collected.

14)The initial and final heads readings and time taken were

noted down.

15)The coefficient of permeability was calculated using the

formula and its average value was found out.

OBSERVATIONS AND CALCULATIONS:

Water content of the soil, w =

Dry density, rd = 1.6g/cc

Height of the mould, h =

Inner diameter of the mould, d =

Volume of the mould ,V =

Diameter of stand pipe, D =

Area of the stand pipe

Cross- sectional area, a =

Area of the mould, A =

Weight of wet soil =

Amount of air dried soil taken =

Water content added =

= 10

= 200ml

Average coefficient of Permeability, K =

SPECIMEN CALCULATIONS:

For observation No. : 1

Initial head reading, h1 =

Final head reading, h2 =

Time taken, t =

Log10

Coefficient of Permeability, K = 2.303aL

RESULT :

Coefficient of permeability of given soil by Falling Head Method =

INFERENCE:


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Since the coefficient of permeability lies between 10 -3and 10-5Cm/s,

the soil is designated as semifervious and has fair drainage properties.

GENERAL REMARKS:

Alternate methods for determination of coefficient of permeability of

a soil are:

A) LABORATORY METHODS:The coefficient of permeability of a soil sample can be determined by

the following laboratory methods:

1) CONSTANT HEAD PERMEABILITY METHOD:

qL

k Ah

Where L = length of specimen

H = head causing flow

q = discharge

A = crosssectional area of specimen

B) FIELD METHODS:

1) PUMPING OUT TEST:

Coefficient of permeability is given for and unconfined aquifer is

2

10

2 1 1

2.30log

2

q rK

b z z r

Where z1= height of water level in observation well (1) at a radial

distance of r1

Z2= height of water level in observation well (2) at a radial

distance of r2

2) PUMPING IN TESTS:

In open end test,

5.5

qK

rH

Where, r = Inner radius of the casing

H = Difference of levels between the inlet of the casing and

the water table.

Q = Discharge

In case of packet tests,

log 102

e

q LK if L r

LH r

1sin 102 2

q LK h if r L

LH r

Where, L = Length of the hole

R = Inner radius of hole

3) INDIRECT METHODS:

Allen Hazens Formula


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7

S.No Soil Type Coefficient of

Permeability

(mm/sec)

Drainage

Properties

1 Clean gravel 10+ to 10+ Very good

2 Coarse and medium

Sands

10- to 10+ Good

3 Fine sands, loose silt 10- to 10- Fair

4 Dense silt, clayey silts 10- to 10- Poor

5 Silty clay, clay 10- to 10- Very poor


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8

DETERMINATION OF KBY CONSTANT HEAD METHOD

AIM:

To determine the permeability of a soil specimen by Constant Head

Permeability Test.

REFERENCE :

IS 2720 : Part 36, 1975.

APPARATUS:

Pemeameter with its accessories, beaker, measuring jar and stop watch.

THEORY:

The coefficient of permeability is equal to the rate of flow of water

through a unit cross sectional area under a unit hydraulic gradient. In the

constant head permeameter , the head causing flow through the specimen

remains constant throughout the test. The coefficient of permeability (K)

is obtained from the relation.

qL QLK

Ah Aht

Where

q= discharge

Q = Total volume of water

H = head causing flow

T = time period

L = Length of the specimen

A = Cross sectional area.

PROCEDURE:

1) The collar of the mould was removed and the interval

dimensions of the mould was measured.

2) From the known water content and the dry density,the

weight of the wet soil occupying the total volume of the

mould was computed.

3) Crease was applied to the inside surface of the mould and

the collar was placed on it.

4) Soil was placed in the mould by compacting it in three

layers. Soil was compacted upto the top surface of the

mould.

5) The mould with the soil is placed on the drainage base

with the porous disc on the top, after inserting a washer in

between.

6) The drainage cap was then placed on the top and it along

with the porous disc was fixed using washers.

7) The constant head reservoir was connected to the drainage

cap inlet.

8) The stop clock was opened and the water was allowed to

flow downward so that all the air was removed.


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9) The stop clock was stopped and water was allowed to flow

through the soil till a steady state was established.

10)The stopwatch was started and the water flowing out of

the base was collected in a measuring flask. The time was

noted after collecting certain discharge.

11)The above process was repeated by changing the head and

the time taken for collecting the same amount of discharge

are noted down.

12)The coefficient of permeability was calculated using above

data and average value was found.

OBSERVATIONS:

Diameter of specimen, d =

Length of the specimen, L =

Cross-sectional area of specimen, A =

Volume of specimen, V = Ah

Dry density, rd =

Water content =

Dry density of the soil required = rd V

Wet weight of the sample = rv

= rd (1+w)V

From table,

Average coefficient of Permeability =

RESULT:

Coefficient of permeability of a soil specimen by constant head

permeameter is

INFERENCE:

Since the permeability of soil is greater than 10-2mm/Sec, the soil is

classified as pervious soil and has good drainage properties.

GENERAL REMARKS:

ALTERNATE METHODS:

The coefficient of permeability can also be determined by the

follo

wing

metho

ds:


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10

LABORATORY METHOD :

FALLING HEAD (OR) VARIABLE HEAD PERMEABILITY

TEST:

For relatively less permeable soils, the quantity of water collected

in the graduated jar of the constant head Permeability test is very small

and cannot be measured accurately. For such soils variable head

permeability test is used.

110

2

2.303log

aL hk

At h

Where, h1= initial head

h2= final head

t = time interval

a = area of cross- section of stand pipe

L = length of the specimen

A = cross- sectioned area of specimen

This method is suitable for very fine sand silt with K = 10-2 to 10-5

mm/Sec.

FIELD METHODS:

PUMPING OUT TEST:

K determined by above methods do not give correct results

since the sample is distributed. The method is extremely useful for a

homogenous, coarse grained deposits and in this test, the soil deposit

over a large area is influenced and the results represent an overall

coefficient of permeability of a large mass of soil.

In case of unconfined aquifer,.

2

102 212 1

2.303log

q hk

hz z

Where r1,r2are radial distances

In case of confined aquifer,

2

10

12 1

2.303log

2

q rk

rb z z

Where Z1 = height of water level in observation well (1) at a

radial distance of r1

Z2 = height of water level in observation well (2) at a

radial distance of r2.

PUMPING IN TESTS:

The pumping in tests gives the value of K of stream

just close to the hole

In case of open end tests K = qWhere r = radius inside of casing

H = difference of levels between the inlet of the casing

and water table.


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In case of Packet Tests,

log 102

e

q Lk if L r

LH r

1

102 2

q Lk Sinh if r L r LH r

The coefficient of permeability can also be determined by

indirect methods and it is used in settlement analysis.

INDIRECT METHODS:

1) ALLENHAZENS FORMULA :

K = CD102

WhereK= Coefficient of permeability (cm/sec)

D10 = Effective size

C = Constant between 100 and 150

2) Kozenycarman equation:

3

2 2.

1

w

s

gk

ec s T

K = Coefficient of permeability

ew= mass density of water (g/ml)

cs = shape factor, 2.5 for granular soils

= Coefficient of viscosity

e = void ratio,

g = 98/cm/ sec2,

T = tortuosity with a value of for granular soils and

s = surface area per unit volume of soil solids.

3) Loudons Formula :

Loudon gave the following empirical formula

Log10 (KS2) = a+bn

S = Specific surface (cm2/cm3) n = porosity,

A = Constant = 1.865 at 100C b = constant = 5.15 at 100C.

4) Consolidation test data:

K = Crrwmv= Crew gmv

Cv: Coefficient of consolidation (m2/sec) g = 9.81 m/sec2

PRACTICAL SIGNIFICANCE:

Permeability is an important engineering property of soil

inorder to find out the settlement, yield of well seepage, etc.

Constant head method is suitable for clear sand and gravel

with

K>10-2mm/s. The falling head permeability test is suitable for fine sand

and silt with K = 10-2to 10-5mm/s.


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For large engineering problems, pumping out test is the usual

practice to measure the permeability of soil by this method. It is apt for

a homogeneous coarse grained soil deposits.

Typical values of the coefficient of Permeability

S.No Soil type Coefficient of

Permeability

(mm/sec)

Drainage

Properties

1

2

3

4

5

Clean gravel

Coarse & medium sands

Fine sands ,loose silt

Dense silt, clayey silts

Silty clay,clay

10+ to 10+

10-2to 10+1

10-4to 10-2

10-5to 10-4

10-8to 10-5

Very good

Good

Fair

Poor

Very poor


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13

DIRECT SHEAR TEST

AIM:

To determine the shear parameters of a sandy soil specimen by

direct shear test.

REFERENCE:

IS : 2720 (Part 13)1972.

APPARATUS:

Shear box divided into two halves by a horizontal plane and

filled with looking and spacing screws, grid plates, loading pad, loading

yoke, proving ring, dial gauge.

THEORY :

Shear strength of a soil is its maximum resistance to shearing

stresses. The shear strength is expressed as

tanC

Where C = Effective cohesion

= Effective stress

= Effective angle of shearing resistance.

PROCEDURE:

1) The internal dimensions of the shear box are measured.

2) The upper part of the box was fixed to the lower part using locking

screws.

3) The soil sample of known density was taken and its weight i.e.

Weight of the sample to be taken was determined from density and

volume.

4) The soil sample was placed in the box and the loading pad was

fixed on the base.

5) The box was mounted on the loading frame.

6) The upper half of the box was brought in contact with the pouring

ring. The contact was checked by giving a light movement.

7) The loading yoke was mounted on the ball placed on loading pad.

8) The weights are placed on the loading yoke to apply a normal load

of 5 lb initially.

9) The sample was allowed to get consolidated under the applied

normal load and all the dial gauges are adjusted to read Zero, the

pouring ring was adjusted to zero.

10)The horizontal shear load was applied at a constant rate of strain

of 0.2mm/min.

11)The readings of the pouring ring was recorded.

12)The test was repeated on identical specimen under the normal

loads of 10,15,20,25 lb.

13)The normal load stress and shear stress are computed and a graph

was drawn between them. The slope of the graph gives the angle

of shearing resistance.

OBSERVATIONS:

Length of shear box =


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Breadth of shear box =

Depth of shear box = 3.7cm

Area of shear box =

Volume of shear box =

Self weight of load hanger =

Lever arm factor =

Dry density of soil, rd= 1.6g/cc

Weight of specimen = rdx volume

Least count of pouring ring =


For observation No :

Normal load = (load x leaver arm factor) +Self weight

Normal stress =Normalload

Area

Shear force at failure = L.C X div

Shear stress =Shear force

Area

1 7avgTan

avg

RESULT:

For the given soil shear parameters are angle of shearing

resistance , 027.47 form graph, c = o and 030.83 from

tabular column.

GENERAL REMARKS:

Direct shear test can be conducted for any one of the three

drainage conditions i.e, UV, CU,CD for UU test. Plain grids are used,

as no time is allowed for consolidation, the test can be conducted

quickly in a few minutes.

For CU test, perforated grids are used. The sample is allowed

to consolidate under the normal load and it is sheared in about 5-10

min.

For CD test, the sample is consolidated under the normal load

and is sheard slowly so that excess pure water pressure is dissipated. A

CD test takes about few hours for cohesionless soils, for cohesive

soils, it may take about 2-5 days.

TRIAXIAL COMPRESSION TEST:

The triaxial test is another method used for the determination

of shear characteristics for all types of soils under different drainage

conditions.

UNCONFINED COMPRESSION TEST:


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The unconfined compression test is a special form of triaxial

test. The test can be conducted on clayey soils which can stand

without confinement and it is generally performed on intact saturated

clays.

VANE SHEAR TEST:

The shear parameters are useful in the following cases:

1) In the stability analysis of slope.2) In determining the lateral earth pressure.3) In determining the bearing capacity of the soils.4) In designing the retaining walls and depths of foundations.Graph


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16

NORTH DAKOTA CONE PENETRATION

TEST

AIM:

To determine the bearing capacity of soil using NORTH DAKOTA CONE

PENETRATION TEST.

REFERENCE:

IS : 2720 (Part 32)1980

APPARATUS:

North Dakota cone, set of weights. Stop clock, hardened steel cone.

GENERAL:

It was developed by North Dakota Highway Development. The test with

North Dakota is simpler and more rapid than CBR test. It is accurate and

has reliable results only in fine grained soils.

SOIL SAMPLE:

6 Kgs of soil sample passing through 4.75 mm IS sieve .

PROCEDURE:

1. The given soil sample was sieved through 4.75 mm IS sieve andabout 6 kg of the soil sample was taken .

2. About 10% of water was added to the sample taken and

thoroughly mixed.

3. The mould with the base plate, collar was taken and a surchargewas placed at the bottom on the base plate.

4. The soil sample was compacted in the mould in 5 layers bygiving 56 blows with a heavy rammer.

5. The collar was then removed and the excess soil wastrimmed to the top level of the mould and the base plate.

Surcharge mass are also removed.

6. The central shaft was mounted vertically and slided freely upand down through collars of two trackets.

7. The central shaft could he located at any revered position bylightening on clamping collar. The graduated plunger which

entered one of the the side supports permits the reading of

the penetration corrected to 1mm.

8. The apparatus was placed in position. The shaft wasunlocked and carefully moved down until the tip of the cone

just touches the surface of sample in mould.

9. The shaft was locked and the reading on the plunger wasnoted.


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10) The shaft was unlocked and simultaneously the stop watch was

made on and the penetration was allowed for one minute.

11) The final reading on the shaft was noted. The difference

between the readings gives the penetration in on under the

weights of moving parts in 5 kg.

TABULAR COLUMN:

Average Bearing Pressure = (33.56+27.49+25.1+27.49)/4

= 28.41 kg/cm2

12) Similarly the above procedure was repeated with the loads of

10kg, 20kg, 40kg and these included 5kg of the moving parts.

OBSERVATIONS:

Weight of the soil sample taken =

Water content added =

CALCULATONS:

The correction to be applied is obtained by the

formula:

C= P40-2P10

Where C= correction to be allied

P40= Penetration at 40 kg load

P10= Penetration at 10 kg load

Bearing area =4

(2Pctan 7

045)2 = 0.0582 Pc2

Where Pc = corrected penetration (am)

C= P40- 102 P

=

Average bearing pressure =


S.No Load

(

k

g

)

Penetration (cm) Corrected

Penetration(cm)

Area

=0.0582Pc2

cm2

Bearing

Pressur

e

Kg/cm2

Initial Final Difference

1 5 4.7 6 1.3 1.6 0.149 33.56

2 10 4.7 6.9 2.2 2.5 0.364 27.49

3 20 4.7 8.1 3.4 3.7 0.797 25.10

4 40 4.7 9.4 4.7 5.0 1.455 27.49


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For observation NO=

Load on the shaft =

Initial Shaft reading =

Final shaft reading =

Penetration = FinalInitial =

Area = 0.0582 Pc2 =

Bearing pressure =Load

Area=

=

RESULT:

The average bearing pressure of soil given by North Dakota

cone test in

GENERAL REMARKS AND PRACTICAL SIGNIFICANCE:

North Dakota is an empirical test and it can be conducted on

untrained samples and compacted samples.

The slows should be uniformly distributed over the surface

of each layer. Clearing and drying of base plate is necessary grease

should be applied to the walls of the mould.

This method is used for the design of flexible pavements

This method helps in finding out the institute bearing

capacity of the subgade.

The method comprises of load penetration test performed in

the laboratory or institute with the empirical design charts to

determine thickness of pavements and its constituent layers.


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15)A graph was driver between load as penetration and the loadscorresponding to 2.5 mm and 5.0 mm are determined and the

corresponding CBR values are determined.

TABULAR COLUMN:

Penetration dial gauge Load dial gauge

S.NO Dial gauge

reading

Penetration(mm)

= Reading L.C 2

Proving

ring

reading

Load in kg

= proving

ring

reading L.C

1 0 0.0 0 0

2 2.5 0.635 10 124.953 50 1.27 26 324.87

4 75 1.905 41 512.30

5 100 2.54 57 712.22

6 125 3.175 71.5 893.40

7 150 3.81 85 1062.08

8 175 4.445 98 1224.5

9 200 5.08 109 1361.96

10 250 6.35 134 1674.3

11 300 7.65 157 1961.7

12 400 10.16 225 2811.413 500 12.70 255 8186.23

OBSERVATIONS:

Diameter of the mould d =

Height of the mould, M =

Least count of proving gauge =

Least count of dial gauge =

=

Volume of the mould, V = 2

4d H

=

Optimum water content =

Mass of empty mould =

Mass of mould + compacted soil =

Mass of compacted soil =

From graph.

Loud at 2.5 mm penetration =

Load at 5.0 mm penetration =

CBR value at 2.5 mm penetration=

CBR value at 5mm penetration = 100tan

Penetration load

S dard load

=RESULT:

California Bearing Ratio of given sample =

GENERAL REMARKS


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UNCONFINED COMPRESSION TEST

AIM

To determine the shear strength of clayey soil remoulded

corresponding to proctors Density.

REFERENCE:

IS : 2720(Part 10)1973

APPARATUS:

Proctors mould with its accessories and unconfined

compression apparatus. Proving ring type, dial gauge weighing

balance over sampling tube split mould of 38 mm dia, 76 mmlong sample extractor knit larger mould.

FORMULAE:

The unconfined compressive strength (qu) is the load per unit

area at which the cylindrical specimen of a cohesive soil fails in

compression

qu = PA

Where P= Axial load at failure

A= Area is corrected area = 0

1

A

Where 0A is the institute area of the specimen

= axial strain =

change inlength

original length

Figure

The undrained shear strength (S) of the soil is equal to are half

of the unconfined compressive strength

S =2

uq

PROCEDURE:

1) Oil was applied to the proctors mould initially the soil sampleabout 3 kg was taken and water content of about 10% was

added.

2) The sample was compacted in the similar manner as theProctors test.

3) The two sampling core wetter tubes are oiled and pushed intothe sample

4) The sampling tube filled with the soil was removed.5) The sample was extruded out of the sampling tube into the splint

mould using the sample extruder and knife.

6) The two ends of the specimen in the split mould was trimmed.


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OBSERVATONS & CALLULATIONS:

Length of the specimen = lo=

Diameter of the specimen = d =

Weight of sample (1)=

Weight of specimen (2)=

Area of specimen = 2

4d

=

Volume of specimen = 2

4d M

=

Least count of dial gauge = 0.01

Least count of proving ring = 100/219lbs

Least of soil taken =No of layers =

No of blows=

% of water added =12

3000 360100

ml

CALCULATIONS:

The unconfined compression strength of given soil sample (1) from

graph (qu1)=

TABULAR COLUMN:

SAMPLE 2

Shear strength of sample (1), S1=1 3.84

2 2

uq = 1.92 kg/cm2

UCC strength of given soil sample (2) from graph,

qu2=

Shear strength of given sample (2) S2=2

2

uq =

Unconfined compressive strength of sample

qavg=

Average cohesion of sample =2

uq

RESULT:

Average unconfined compressive strength of given soil sample , qu=

Cohesion of a given soil sample =

ALTENATE METHODS:

The following are the methods of determining the their strength of

clayey soils.

1) DIRECT SHEAR TEST:

The direct sheen test is conducted on cohesion less soils as CDtest but it is occasional used to determine the strength parameters

of clay under unconsolidated untrained and consolidated drained


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condition. But it does not after flexibility of a triaxial

compression test.

2) TRIAXIAL SHEAR TEST:

The triaxial test is another method used for the determination of

shear characteristics of all types of solids under different

drainage conditions.

3) UNCONFINED COMPRESSION TEST:

The unconfined compression test is a special form of triennial

test and it is generally performed on intact saturated clays.

4) VANE SHEAR TEST:

The untrained shear strength of soft clays can be determined by

this test

S=2

3[ ]2

T

D HD

where T = Torque applied

GENERAL REMARKS:

The shear parameters are useful in the following cases:

In the stability analysis of the slope In determining the earth pressures laterally In determining the bearing capacity of soils In the design of retaining walls and in estimating or Calculating the depth of foundation etc.

In assessing sensitivity of soils.Graph :1

Graph :2


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TRIAXIAL SHEAR TEST

AIM

To determine the shear parameters of the soil specimen by

triaxial shear test.

REFERENCE:

IS : 2750 (Part 13)1986

ASTH D 3080

APPARATUS:

Triaxial cell rubber membrane O rings porous stones loading

frame proving ring (LVDTfor deformation measurement)

PROCEDURE:

1. The given soil sample was compacted in the similar process ofproctors test and samples were taken by pushing sampling tubes

into the specimen.

2. The sample was extracted out of the sampling tube into the splitmould using sample extractor and knife.

3. The two ends of the specimen in the split mould was trimmedand was removed by splitting mould into two parts.

4. A porous stone was enclosed in a rubber membrane which wassealed to the specimen with the help of O rings.

5. The loading machine was spirited on and the cell pressure wassent to 0.5 kg/cm2initially.

6. The sensor for measuring deformation deformation of thesample is LVDT.

7. The LVDT for measuring Arial deformation of the specimenwas set to 12.5 mm

8. The loading readings were taken correspondingly todeformations of 0.5,1,1.5,..

9. The loading was stopped after the completion of the test ie,when the sample fails.

10.The test was repeated on two more samples extracted from somemould for cell pressure 1.0 kg/cm2by adding corresponding

weights on loading machine.

OBSERVATIONS:

Diameter of specimen, d =

Length of specimen, L=

Area of specimen = A0 =2

4

d

=

Least count of dial gauge = 1 div = 0.01 mm

Least count of proving ring = 1div = 2.54 N

Weight of wet soil =


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Weight of dry soil =

FORMULA:

T3= Minor principal stress

T1= Major principal stress

Deviator stress = Td=Load

Connected area

Corrected area =0

1

A

E

Where A0= Original area

L = Deformation

L = Length of specimen

CALCULATIONS

From graph:

Deviator stress (for T31) =



Major principal stress T11= T31+ Td 1

=

Major principal stress, T12= T31+ Td 2

Major principal stress, T13= T33+ Td3

=

From

T1=2

1 3 tan 2 tanT T c

20.5 tan 2 tan (1)x c

21.0 tan 2 tan (2)y c

21.5 tan 2 tan (3)z c

Average of C=

Average of =

RESULT:

From calculations:

Shear parameters, C =

=

From graph, C=

=

GENERAL REMARKS:


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1) Merits:i) The test is convenient simple and quickii) Ideally suited for measuring unconfined shear strength of intact

saturated clays.

iii)The sensitivity of soil may he determined.Demerits:

1) The test can be conducted on saturated clays/ fissure clays.2) The test may be misleading for soils for which angle of shearing

resistance is not zero.

Vane Shear Test:The shear strength is given by

32

( )2 6

TS

H DD

Where T = Torque applied

d= diameter

H= Height of the vane

Graph:1

Graph: 2


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CONSOLIDATION TEST

AIM:

To determine the consolidation characteristics of a soil

REFERENCE:

IS : 2720(Part 15)-1965

APPARATUS:

Consolidometer with a loading device specimen ring water

reservoir to saturate the sample porous stones knife weighing

balance over steel ball dial gauge large container.

PROCEDURE:1) The metal ring was cleaned and dried, its diameter, height mass

height mass of the empty ring is measured

2) The ring was pushed into the soil and these removed andspecimen was thinned with tops and bottom of ring

3) The consolidometer was assembled and the bottom porous stonebottom fitter paper specimen top filter paper specimen, and

porous stone were placed are by one

4) The loading block was placed exactly at the top of the porousstone.

5) The mould assembled was mounted on the loading fames aplaced such that the load applied was axial.

6) An initial reading load of 5 KN/M2 pressure was applied andfinal gauge reading was taken after 24 hours.

7) The load was increased to a pressure of 10,20,40,80,160,320KN/M2

8) The load was decreased to 14

th

of the previous load and the dial

gauge readings were noted after 24 hours.

9) Finally the means of ring with the specimen was taken and watercontent was determined.

OBSERVATIONS & CALCULATIONS:

Height of the specimen = H0=

Diameter of the sample =

Empty weight of ring, w1=

Weight of empty ring + wet soil, w2 =

Weight of empty ring + dry soil, w3=

Area of the specimen, A = 2604 =

=

Specific gravity, G = 2.68


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Weight of solids, HS=S

w

W

Gr A=

=

Final water content, Wf= 2 3

3 1

W W

W W

=

Final void ratio, ef = Wf G

=

= 1.07

RESULT:

From graph, height of solids method

Compression index, CC=

Coefficient of consolidation, CV=

Preconsolidation pressure = JC=

Squalling index, CS=

Square root of time method:

From graph:

Coefficient of consolidation = CV=

GENERAL REMARKS AND PRACTICAL SIGNIFICANCE:

The degree of consolidation depends upon the time factor TV,

given by

TV= 2VC T

d

The compression index of a normally consolidated soil is

constant and settlement is given by

logCf o o

o

CS H T T

He

The coefficient of permeability is obtained by using

V

w w

kC

ge M

The liquid limit of a specimen can be obtained by knowing thecompression index by

CC= 0.009 (WL-10)- Undisturbed samples

= (0.007) (WL-10)- Remoulded samples

Graph : 1

Graph : 2

1)

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