Geo tech lab

GEOTECHNICAL ENGINEERING LAB
EXPERIMENTS
From: Er. Love Sharma
Shri Mata Vaishno Devi University, Katra, Jammu

DETERMINATION OF MOISTURE CONTENT
Apparatus :
 Non-corrodible air-tight container.
 Electric oven.
 Balance of sufficient sensitivity.
Procedure :
 Clean the container with lid dry it and weigh it.
 Take sample in the container and weigh and Keep the container in the oven.
 Dry the specimen to constant weight maintaining the temperature between 1050C to 1100C for a
period varying with the type of soil but usually 16 to 24 hours.
 Record the final constant weight of the container with dried soil sample.
Technical Discussion:
 In almost all soil tests natural moisture content of
the soil is to be determined.
 To sight a few, natural moisture content is used in
determining the bearing capacity and settlement.
 The natural moisture content will give an idea of the
state of soil in the field.
 The knowledge of the natural moisture content is
essential in all studies of soil mechanics.
Overview: The natural moisture content is the ratio of the weight of water to the weight of the solids in a
given mass of soil. This ratio is usually expressed as percentage. (Reference: IS: 2720 Part 2-1973)
E l e c t r i c O v e n
Soil Sample
Container
 Moisture Content =
Weight of water
Weight of oven dry soil
x 100

DETERMINATION OF SPECIFIC GRAVITY
Apparatus :
 Pycnometer
 IS Sieve(4.75 mm)
 Vacuum pump & Glass rod
 Electric Oven
 Weighing balance
Procedure :
 Dry the pycnometer and weigh it with its cap (W1).
 Take about 200 g to 300 g of soil into the pycnometer and weigh
again(W2).
 Fill the pycnometer with water and weigh it (W3).
 Clean the pycnometer and filled with water again and weigh it (W4).
 After receiving the soil sample it is dried in oven at a temperature of 105 to
1150C for a period of 16 to 24 hours.
 The specific gravity values of the soil will be reported at 270 Celsius.
 Specific Gravity, G =
(W2 −W1)
W2 − W1 − (W3 −W4)
 The specific gravity of soil particles will come within the range of 2.65 to
2.85.
 If the soils consist of porous and organic materials, a specific gravity value
of less than 2 will be obtained.
 A specific gravity value greater than 3 will be shown by soils that have
heavy substances.
Overview: Specific gravity (G) is defined as the ratio of weight of given volume of dry soil solids to the
weight of an equal volume of distilled water at 40 C. It helps in the calculation of void ratio, degree of
saturation and other different soil properties. (Reference: IS: 2720 Part 3-1980)
P Y C N O M E T E R

SIEVE ANALYSIS OF SOIL
Apparatus :
 IS Sieves with sieve shaker
 Weighing balance.
Procedure :
 The sample is dried in the oven at a temperature of 1050
C to 1100 C.
 The oven dry sample is weighed and sieved
successively on the appropriate sieves starting with
largest.
 Each sieve is shaken for a period of not less than 2 min.
 On completion of sieving the material retained on each
sieve is weighed.
Overview: Sieve analysis is a technique used to determine the particle size distribution of a given soil.
(Reference: IS: 2720 Part 4-1985)
IS – S I E V E S
 The grain size analysis is widely used in classification of soils.
 The data obtained from grain size distribution curves is used in the design of filters for earth dams and
to determine suitability of soil for road construction, air field etc.
 Information obtained from grain size analysis can be used to predict soil water movement although
permeability tests are more generally used.
 Draw graph between log sieve size v/s percentage finer.
The graph is known as grading curve.
 The percent finer is calculated by subtracting the
cumulative percent retained from 100 percent.

DETERMINATION OF LIQUID LIMIT
Apparatus :
 Casagrande apparatus
 IS Sieve [425 micron]
 Electric oven
 Weighing balance
Procedure :
 Add distilled water into the 250 gm. dry soil.
 Place a portion of the paste in the cup of apparatus.
 Cut a groove along the centre line of soil pat in the cup.
 Turn the handle at the rate of two revolutions/sec. and
count blow until the two halves of soil come into
contact for a length of about 12 mm.
 Take soil from the cup for water content determination.
 Repeat the test with different moisture contents at least
three more times.
Overview: The Liquid Limit (LL) is the moisture content at which a fine-grained soil no longer flows
like a liquid. At this limit the soil possess low shear strength. (Reference: IS: 2720 Part 5-1985)
 Plot the graph between water content & number of blows
and read moisture content at 25 blows is the value of
liquid limit.
 Liquid limit is significant to know the stress history and
general properties of the soil met with construction.
 From the results of liquid limit the compression index may
be estimated. The compression index value will help us in
settlement analysis
C A S A G R A N D E
A P P A R A T U S

DETERMINATION OF PLASTIC LIMIT
Apparatus:
 Electric oven
 Sieve [425 micron]
 Balance (0.01 g accuracy)
 Flat glass surface for rolling
Procedure:
 Take a soil sample of 20 g and mixed it with water.
 10 g of the above plastic mass is to be taken and roll the
mass into a thread (the rate of rolling shall be between
60 to 90 stokes/minute) till the thread becomes 3 mm.
in diameter.
 The process is to be continued until the thread
crumbled with the diameter of 3 mm.
 The pieces of the crumbled thread are to be collected in
a air tight container for moisture content determination.
Overview: The plastic limit of a soil is the moisture content at which soil begins to behave as a plastic
material. A soil is considered non-plastic if a thread cannot be rolled out down to 3.2 mm at any moisture.
(Reference: IS: 2720 Part 5-1985)
 The plastic limit is defined as the water content at which a
soil will just begin to crumble when rolled into a thread of
3mm in diameter.
 The value of plastic limit and liquid limit are used to
classify fine grained soil.
 The values of plastic limit and liquid limit are used to
calculate flow index, toughness index and plasticity index
of the soil.
S E T O F
P L A S T I C L I M I T

PROCTOR COMPACTION TEST
Apparatus:
 Cylindrical mould & Rammer
 Balance & IS Sieves
 Mixing tray & Trowel
 Graduated cylinder, etc.
Procedure:
 5 Kg. of soil is taken and the water is added to it.
 Fill the moist soil into the mould and compact it in three equal
layers (each layer being given 25 blows from the 2.6 kg
rammer dropped from a height of 310 mm above the soil) and
weight it.
Overview: The Proctor compaction test is a laboratory method of experimentally determining the
optimum moisture content at which a given soil type will become most dense and achieve its maximum
dry density. (Reference: IS: 2720 Part 7-1980)
 Wet density (g/cc) =
weight of compacted soil
Volume of mould
 Dry density (g/cc) =
Wet Density
1+water content of soil
 Plot the dry density against moisture content and find out the maximum
dry density and optimum moisture for the soil.
 Adequate period (about 15 minutes for clayey soils and 56 minutes for
coarse grained soils) is allowed after mixing the water.
Cylindrical Mould
& Rammer
 The soil is removed from the mould and take some soil for water
content determination.
 Repeat the whole procedure, after adding suitable amount of water to
the soil in an increasing order.

SHEAR STRENGTH TEST
Apparatus:
 Direct Shear Test Apparatus with shear box
 Porous stone, grid plate & Straight edge.
 Weighing balance & IS Sieve.
 Loading frame, Proving ring, Dial gauge, etc.
Procedure:
 The soil is placed into the shear box and the upper
grid plate, porous stone and loading pad is placed in
sequence on the soil specimen.
 The box is placed inside its container and is mounted
on the loading frame.

 The motor is started with a selected speed and shear
load is applied at a constant rate of strain.
 Readings of the gauges are taken until the horizontal
shear load peaks and then falls, or the horizontal
displacement reaches 20% of the specimen length.
 The test is repeated on identical specimens under
different normal stress values.
Overview: Shear strength is a term used in soil mechanics to describe the magnitude of the shear stress that
a soil can sustain. Direct shear test is used to determine the shear strength of the soil. It is more suitable for
cohesionless soils (Reference: IS: 2720 Part 13-1986)
DIRECT SHEAR TEST APPARATUS
The Shear Strength (s) is expressed as:
S = C + σ tan Ø
Where:
C = Cohesion, σ = Normal Stress
Ø = Angle of shearing resistance.

 Plot a graph between normal stress and shear stress
by taking normal stress on abscissa and shear stress
at failure on ordinate.
 The graph looks like as shown below.
 From the graph cohesion (C) and angle of shearing
resistance (Ø) can be known
 Shear strength (S) can be calculated from the
formula: S = C + σ tan Ø.
 The dial readings are converted to the appropriate
displacement and load units by multiplying with
respective least counts.
 Shear strains are calculated by dividing horizontal
displacements with the specimen length, and shear
stresses are obtained by dividing horizontal shear
forces with the shear area.
This test can be performed in three
different drainage conditions namely:
 Unconsolidated-Undrained (UU)
 Consolidated-Undrained (CU)
 Consolidated-Drained (CD)
Shear Box, Porous Stones,
Grid Plates & Loading pad

Geo tech lab

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Geo tech lab

Similar to Geo tech lab (20)

Recently uploaded

Recently uploaded (20)

Geo tech lab