EXPERIMENT 1
WATER CONTENT DETERMINATION
Purpose:
This test is performed to determine the water (moisture) content of soils. The water
content is the ratio, expressed as a percentage, of the mass of “pore” or “free” water in a
given mass of soil to the mass of the dry soil solids.
Standard Reference:
ASTM D 2216 - Standard Test Method for Laboratory Determination of
Water (Moisture) Content of Soil, Rock, and Soil-Aggregate Mixtures
Significance:
For many soils, the water content may be an extremely important index used for
establishing the relationship between the way a soil behaves and its properties. The
consistency of a fine-grained soil largely depends on its water content. The water content
is also used in expressing the phase relationships of air, water, and solids in a given
volume of soil.
Equipment:
Drying oven: thermostatically-controlled, preferably of the forced-draft type, meeting
the requirements of Specification E 145 and capable of maintaining a uniform
temperature of 110 ± 5°C throughout the drying chamber.
Balance: All balances must meet the requirements of Specification D 4753 and this
section. A Class GP1 balance of 0.01g readability is required for specimens having a
mass of up to 200 g
Container Handling Apparatus, gloves, tongs, Spatula, or suitable holder for moving and
handling hot containers after drying.
Test Procedure:
Step1: Record the moisture can and lid number. Determine and record the mass of an empty,
clean, and dry moisture can with its lid (MC)
Step2: Place the moist soil in the moisture can and secure the lid. Determine and record the
mass of the moisture can (now containing the moist soil) with the lid (MCWS).
Step3: Remove the lid and place the moisture can (containing the moist soil) in the drying
oven that is set at 105 °C. Leave it in the oven overnight.
Step4: Remove the moisture can. Carefully but securely, replace the lid on the moisture can
using gloves, and allow it to cool to room temperature. Determine and record the
mass of the moisture can and lid (containing the dry soil) (MCDS).
Step5: Empty the moisture can and clean the can and lid.
Data Analysis:
Calculate the water content of the material as follows:
1) Determine the mass of soil solids.
2) Determine the mass of pore water.
3) Determine the water content.
10
EXAMPLE DATA
WATER CONTENT DETERMINATION
Date Tested:
Tested By:
Project Name:
Sample Number:
Sample Description:
Specimen number
Moisture can and lid number
MC = Mass of empty, clean can + lid (g)
MCWS = Mass of can, lid, and moist soil (g)
MCDS = Mass of can, lid, and dry soil (g)
MS = Mass of soil solids (g)
MW = Mass of pore water (g)
w = Water content, w%
1
2
3
EXPERIMENT 2
DETERMINATION OF SPECIFIC GRAVITY
OBJECTIVE
Determine the specific gravity of soil fraction passing 4.75 mm I.S sieve by density bottle.
NEED AND SCOPE
The knowledge of specific gravity is needed in calculation of soil properties like void ratio,
degree of saturation etc.
DEFINITION
Specific gravity G is defined as the ratio of the weight of an equal volume of distilled water
at that temperature both weights taken in air.
APPARATUS REQUIRED
1. Density bottle of 50 ml with stopper having capillary hole.
2. Balance to weigh the materials (accuracy 10gm).
3. Wash bottle with distilled water.
4. Alcohol and ether.
PROCEDURE
1. Clean and dry the density bottle
a. wash the bottle with water and allow it to drain.
b. Wash it with alcohol and drain it to remove water.
c.
Wash it with ether, to remove alcohol and drain ether.
2. Weigh the empty bottle with stopper (W1)
3. Take about 10 to 20 gm of oven soil sample which is cooled in a desiccator. Transfer it to
the bottle. Find the weight of the bottle and soil (W2).
4. Put 10ml of distilled water in the bottle to allow the soil to soak completely. Leave it for
about 2 hours.
5. Again fill the bottle completely with distilled water put the stopper and keep the bottle
under constant temperature water baths (Tx0 ).
6. Take the bottle outside and wipe it clean and dry note. Now determine the weight of the
bottle and the contents (W3).
7. Now empty the bottle and thoroughly clean it. Fill the bottle with only disttiled water and
weigh it. Let it be W4 at temperature (Tx0 C).
8. Repeat the same process for 2 to 3 times, to take the average reading of it.
OBSERVATIONS
S. No.
Observation Number
1
Weight of density bottle (W1 g)
2
Weight of density bottle + dry soil
(W2 g)
Weight of bottle + dry soil + water
3
at temperature T x0 C (W3 g)
Weight of bottle + water (W4 g) at
4
temperature Tx0 C
Specific gravity G at Tx0 C
Average specific gravity at Tx0 C
CALCULATIONS
1
2
3
INTERPRETATION AND REPORTING
Unless or otherwise specified specific gravity values reported shall be based on water at
270C. So the specific gravity at 270C = KSp. gravity at Tx0C.
The specific gravity of the soil particles lie with in the range of 2.65 to 2.85. Soils
containing organic matter and porous particles may have specific gravity values below 2.0.
Soils having heavy substances may have values above 3.0.
EXPERIMENT 3
GRAIN SIZE ANALYSIS
(SIEVE AND HYDROMETER ANALYSIS)
Purpose:
This test is performed to determine the percentage of different grain sizes contained
within a soil. The mechanical or sieve analysis is performed to determine the
distribution of the coarser, larger-sized particles, and the hydrometer method is used to
determine the distribution of the finer particles.
Standard Reference:
ASTM D 422 - Standard Test Method for Particle-Size Analysis of Soils
Significance:
The distribution of different grain sizes affects the engineering properties of soil. Grain
size analysis provides the grain size distribution, and it is required in classifying the
soil.
Equipment:
Balance
Set of sieves
Cleaning brush
Sieve shaker
Mixer (blender)
152H Hydrometer
Sedimentation cylinder
Control cylinder
Thermometer
Beaker
Timing device.
Test Procedure:
Sieve Analysis:
Step1: Write down the weight of each sieve as well as the bottom pan to be used in the
analysis.
Step2: Record the weight of the given dry soil sample.
Step3: Make sure that all the sieves are clean, and assemble them in the ascending order of
sieve numbers (#4 sieve at top and #200 sieve at bottom). Place the pan below #200
sieve. Carefully pour the soil sample into the top sieve and place the cap over it.
Step4: Place the sieve stack in the mechanical shaker and shake for 10 minutes.
Step5 Remove the stack from the shaker and carefully weigh and record the weight of each
sieve with its retained soil. In addition, remember to weigh and record the weight of
the bottom pan with its retained fine soil.
Hydrometer Analysis:
Step1: Take the fine soil from the bottom pan of the #200 sieve set, place it into a beaker, and
add 125 mL of the dispersing agent (sodium hexametaphosphate (40 g/L)) solution.
Stir the mixture until the soil is thoroughly wet. Let the soil soak for at least ten
minutes.
Step2: While the soil is soaking, add 125mL of dispersing agent into the control cylinder and
fill it with distilled water to the mark. Take the reading at the top of the meniscus
formed by the hydrometer stem and the control solution. A reading less than zero is
recorded as a negative (-) correction and a reading between zero and sixty is
recorded as a positive (+) correction. This reading is called the zero correction. The
meniscus correction is the difference between the top of the meniscus and the level
of the solution in the control jar (Usually about +1). Shake the control cylinder in
such a way that the contents are mixed thoroughly. Insert the hydrometer and
thermometer into the control cylinder and note the zero correction and temperature
respectively.
Step3: Transfer the soil slurry into a mixer by adding more distilled water, if necessary, until
mixing cup is at least half full. Then mix the solution for a period of two minutes.
Step4: Immediately transfer the soil slurry into the empty sedimentation cylinder. Add
distilled water up to the mark.
Step5: Cover the open end of the cylinder with a stopper and secure it with the palm of your
hand. Then turn the cylinder upside down and back upright for a period of one
minute. (The cylinder should be inverted approximately 30 times during the
minute.)
Step6: Set the cylinder down and record the time. Remove the stopper from the cylinder.
After an elapsed time of one minute and forty seconds, very slowly and carefully
insert the hydrometer for the first reading.
(Note: It should take about ten seconds to insert or remove the hydrometer to minimize any
disturbance, and the release of the hydrometer should be made as close to the
reading depth as possible to avoid excessive bobbing).
Step7: The reading is taken by observing the top of the meniscus formed by the suspension
and the hydrometer stem. The hydrometer is removed slowly and placed back into
the control cylinder. Very gently spin it in control cylinder to remove any particles
that may have adhered.
Step8: Take hydrometer readings after elapsed time of 2 and 5, 8, 15, 30, 60 minutes and 24
hours
Data Analysis:
Sieve Analysis:
(1) Obtain the mass of soil retained on each sieve by subtracting the weight of the
empty sieve from the mass of the sieve + retained soil, and record this mass as the
weight retained on the data sheet. The sum of these retained masses should be
approximately equals the initial mass of the soil sample. A loss of more than two
percent is unsatisfactory.
(2) Calculate the percent retained on each sieve by dividing the weight retained on each
sieve by the original sample mass.
(3) Calculate the percent passing (or percent finer) by starting with 100 percent and
subtracting the percent retained on each sieve as a cumulative procedure.
The graded depending upon the value of coefficient of curvature and uniformly
coefficient. Coefficient of curvature may be estimated as:
.
Where,
D60=diameter at 60% finer
D30=diameter at 30% finer
D10=diameter at 10% finer
It should lie between 1 and 2 for well graded gravels and sands
Uniformity coefficient
Determination No.
1
2
3
D60
D30
D10
Cc
Cu
Hydrometer Analysis:
(1) Apply meniscus correction to the actual hydrometer reading.
(2) From Table 1, obtain the effective hydrometer depth L in cm (for meniscus
corrected reading).
(3) For known Gs of the soil (if not known, assume 2.65 for this lab purpose), obtain
the value of K from Table 2.
(4) Calculate the equivalent particle diameter by using the following formula:
D
K
L
t
Where t is in minutes, and D is given in mm.
(5) Determine the temperature correction CT from Table 3.
(6) Determine correction factor “a” from Table 4 using Gs.
(7) Calculate corrected hydrometer reading as follows:
Rc = RACTUAL - zero correction + CT
(8) Calculate percent finer as follows:
P
R Xa
X100
W
Where WS is the weight of the soil sample in grams.
(9) Adjusted percent fines as follows:
P
AXF
100
F200 = % finer of #200 sieve as a percent
(10) Plot the grain size curve D versus the adjusted percent finer on the semilogarithmic
sheet.
Table 1. Values of Effective Depth Based on Hydrometer and Sedimentation Cylinder
of Specific Sizes
Hydrometer 151H
Actual
Hydrometer
Reading
1,000
1,001
1,002
1,003
1,004
1,005
1,006
1,007
1,008
1,009
1,010
1,011
1,012
1,013
1,014
1,015
1,016
1,017
1,018
1,019
1,020
1,021
1,022
1,023
1,024
1,025
1,026
1,027
1,028
1,029
1,030
1,031
1,032
1,033
1,034
1,035
1,036
1,037
1,038
1.039
Hydrometer 151H
Effective
Actual
Depth,
L, Hydrometer
cm
Reading
16,3
0
16
1
15,8
2
15,5
3
15,2
4
15
5
14,7
6
14,4
7
14,2
8
13,9
9
13,7
10
13,4
11
13,1
12
12,9
13
12,6
14
12,3
15
12,1
16
11,8
17
11,5
18
11,3
19
11,0
20
10,7
21
10,5
22
10,2
23
10,0
24
9,7
25
9,4
26
9,2
27
8,9
28
8,6
29
8,4
30
8,1
7,8
7,6
7,3
7,0
6,8
6,5
6,2
5,9
Effective
Actual
Depth,
L, Hydrometer
cm
Reading
16.3
31
16.1
32
16.0
33
15.8
34
15.6
35
15.5
36
15.3
37
15.2
38
15.0
39
14.8
40
14.7
41
14.5
42
14.3
43
14.2
44
14.0
45
13.8
46
13.7
47
13.5
48
13.3
49
13.2
50
13.0
51
12.9
52
12.7
53
12.5
54
12.4
55
12.2
56
12.0
57
11.9
58
11.7
59
11.5
60
11.4
Effective
Depth,
L, cm
11.2
11.1
10.9
10.7
10.6
10.4
10.2
10.1
9.9
9.7
9.6
9.4
9.2
9.1
8.9
8.8
8.6
8.4
8.3
8.1
7.9
7.8
7.6
7.4
7.3
7.1
7.0
6.8
6.6
6.5
Table 2. Values of k for Use in Equation for Computing Diameter of Particle in Hydrometer
Analysis
Temp. C
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Specific Gravity of Soil Particles
2.45
2.50
2.55
2.60
2.65
2.70
2.75
2.80
2.85
.01510
.01511
.01492
.01474
.01456
.01438
.01421
.01404
.01388
.01372
.01357
.01342
.0127
.01312
.01298
.01505
.01486
.01467
.01449
.01431
.01414
.01397
.01381
.01365
.01349
.01334
.01319
.01304
.01290
.01276
.01481
.01462
.01443
.01425
.01408
.01391
.01374
.01358
.01342
.01327
.01312
.01297
.01283
.01269
.01256
.01457
.01439
.01421
.01403
.01386
.01369
.01353
.01337
.01321
.01306
.01291
.01277
.01264
.01249
.01236
.01435
.01417
.01399
.01382
.01365
.01348
.01332
.01317
.01301
.01286
.01272
.01258
.01244
.01230
.01217
.01414
.01396
.01378
.01361
.01344
.01328
.01312
.01297
.01282
.01267
.01253
.01239
.01225
.01212
.01199
.01394
.01376
.01359
.01342
.01325
.01390
.01294
.01279
.01264
.01249
.01235
.01221
.01208
.01195
.01182
.01374
.01356
.01339
.01323
.01307
.01291
.01276
.01261
.01246
.01232
.01218
.01204
.01191
.01178
.01165
.01356
.01338
.01321
.01305
.01289
.01273
.01258
.01243
.01229
.01215
.01201
.01188
.01175
.01162
.01149
Table 3. Temperature Correction Factors CT
Temperature
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
factor CT
1.10
-0.90
-0.70
-0.50
-0.30
0.00
+0.20
+0.40
+0.70
+1.00
+1.30
+1.65
+2.00
+2.50
+3.05
+3.80
Table 4. Correction Factors a for Unit Weight of Solids
Unit Weight of
Correction
Soil Solids, g/cm3
Factor a
2.85
2.80
2.75
2.70
2.65
2.60
2.55
2.50
0.96
0.97
0.98
0.99
1.00
1.01
1.02
1.04
EXPERIMENT 4
ATTERBERG LIMITS
Purpose:
This lab is performed to determine the plastic and liquid limits of a fine-grained soil. The
liquid limit (wL) is arbitrarily defined as the water content, in percent, at which a pat of soil
in a standard cup and cut by a groove of standard dimensions will flow together at the base of
the groove for a distance of 13 mm (1/2 in.) when subjected to 25 shocks from the cup being
dropped 10 mm in a standard liquid limit apparatus operated at a rate of two shocks per
second. The plastic limit (wP) is the water content, in percent, at which a soil can no longer
be deformed byrolling into 3.2 mm 1/8 in.) diameter threads without crumbling.
Standard Reference:
ASTM D 4318 - Standard Test Method for Liquid Limit, Plastic Limit, and
Plasticity Index of Soils
Significance:
The Swedish soil scientist Albert Atterberg originally defined seven “limits of consistency”
to classify fine-grained soils, but in current engineering practice only two of the limits, the
liquid and plastic limits, are commonly used. (A third limit,called the shrinkage limit, is used
occasionally.) The Atterberg limits are based on the moisture content of the soil. The plastic
limit is the moisture content that defines where the soil changes from a semi-solid to a plastic
(flexible) state. The liquid limit is the moisture content that defines where the soil changes
from a plastic to a viscous fluid state. The shrinkage limit is the moisture content that defines
where the soil volume will not reduce further if the moisture content is reduced. A wide
variety of soil engineering properties have been correlated to the liquid and plastic limits, and
these Atterberg limits are also used to classify a fine-grained soil according to the Unified
Soil Classification system or AASHTO system.
Equipment:
- Casagrand apparatus
- Porcelain (evaporating) dish
- Flat grooving tool with gage
- Eight moisture cans
- Balance
- Glass plate
- Spatula
- Wash bottle filled with distilled water
- Oven set at 105°C.
Test Procedure:
Liquid Limit:
(1) Take roughly 3/4 of the soil and place it into the porcelain dish. Assume that the soil was
previously passed though a No. 40 sieve, air-dried, and then pulverized. Thoroughly mix the
soil with a small amount of distilled water until it appears as a
smooth uniform paste. Cover the dish with cellophane to prevent moisture from escaping.
(2) Weigh four of the empty moisture cans with their lids, and record the respective weights
and can numbers on the data sheet.
(3) Adjust the Casagrand apparatus by checking the height of drop of the cup. The point on
the cup that comes in contact with the base should rise to a height of 10 mm. The block on
the end of the grooving tool is 10 mm high and should be used as a gage. Practice using the
cup and determine the correct rate to rotate the crank so that the cup drops approximately two
times per second.
(4) Place a portion of the previously mixed soil into the cup of the Casagrand apparatus at the
point where the cup rests on the base. Squeeze the soil down to eliminate air pockets and
spread it into the cup to a depth of about 10 mm at its deepest point. The soil pat should form
an approximately horizontal surface (See Photo B).
(5) Use the grooving tool carefully cut a clean straight groove down the center of the cup.
The tool should remain perpendicular to the surface of the cup as groove is being made. Use
extreme care to preventsliding the soil relative to the surface of the cup (See Photo C).
(6) Make sure that the base of the apparatus below the cup and the underside of the cup is
clean of soil. Turn the crank of the apparatus at a rate of approximately two drops per second
and count the number of drops, N, it takes to make the two halves of the soil pat come into
contact at the bottom of the groove along a distance of 13 mm (1/2 in.) (See Photo D). If the
number of drops exceeds 50, then go directly to step eight and do not record the number of
drops, otherwise, record the number of drops on the data sheet.
(7) Take a sample, using the spatula, from edge to edge of the soil pat. The sample should
include the soil on both sides of where the groove came into contact. Place the soil into a
moisture can cover it. Immediately weigh the moisture can containing the soil, record its
mass, remove the lid, and place the can into the oven. Leave the moisture can in the oven for
at least 16 hours. Place the soil remaining in the cup into the porcelain dish. Clean and dry
the cup on the apparatus and the grooving tool.
(8) Remix the entire soil specimen in the porcelain dish. Add a small amount of distilled
water to increase the water content so that the number of drops required to close the groove
decrease.
(9) Repeat steps six, seven, and eight for at least two additional trials producing successively
lower numbers of drops to close the groove. One of the trials shall be for a closure requiring
25 to 35 drops, one for closure between 20 and 30 drops, and one trial for a closure requiring
15 to 25 drops. Determine the water content from each trial by using the same method used
in the first laboratory. Remember to use the same balance for all weighing.
Plastic Limit:
(1) Weigh the remaining empty moisture cans with their lids, and record the respective
weights and can numbers on the data sheet.
(2) Take the remaining 1/4 of the original soil sample and add distilled water until the soil is
at a consistency where it can be rolled without sticking to the hands.
(3) Form the soil into an ellipsoidal mass (See Photo F). Roll the mass
between the palm or the fingers and the glass plate (See Photo G). Use sufficient pressure to
roll the mass into a thread of uniform diameter by using about 90 strokes per minute. (A
stroke is one complete motion of the hand forward and back to the starting position.) The
thread shall be deformed so that its diameter reaches 3.2 mm (1/8 in.), taking no more than
two minutes.
(4) When the diameter of the thread reaches the correct diameter, break the thread into
several pieces. Knead and reform the pieces into ellipsoidal masses and re-roll them.
Continue this alternate rolling, gathering together, kneading and re-rolling until the thread
crumbles under the pressure required for rolling and can no longer be rolled into a 3.2 mm
diameter thread (See Photo H).
(5) Gather the portions of the crumbled thread together and place the soil into a moisture can,
then cover it. If the can does not contain at least 6 grams of soil, add soil to the can from the
next trial (See Step 6). Immediately weigh the moisture can containing the soil, record its
mass, remove the lid, and place the can into the oven. Leave the moisture can in the oven for
at least 16 hours.
(6) Repeat steps three, four, and five at least two more times. Determine the water content
from each trial by using the same method used in the first laboratory. Remember to use the
same balance for all weighing.
Analysis:
Liquid Limit:
(1) Calculate the water content of each of the liquid limit moisture cans after they have been
in the oven for at least 16 hours.
(2) Plot the number of drops, N, (on the log scale) versus the water content (w). Draw the
best-fit straight line through the plotted points and determine the liquid limit (wL) as the
water content at 25 drops.
Plastic Limit:
(1) Calculate the water content of each of the plastic limit moisture cans after they have been
in the oven for at least 16 hours.
(2) Compute the average of the water contents to determine the plastic limit, PL. Check to
see if the difference between the water contents is greater than the acceptable range of two
results (2.6 %).
(3) Calculate the plasticity index, IP=wL-wP. Report the liquid limit, plastic limit, and
plasticity index to the nearest whole number, omitting the percent designation.
EXPERIMENT 5
STANDARD TEST METHODS FOR LABORATORY COMPACTION
CHARACTERISTICS OF SOIL
Purpose:
These test methods covers laboratory compaction methods used to determine the
relationship between water content and dry unit weight of soils (compaction curve)
compacted in a 4 or 6-in. (101.6 or 152.4-mm) diameter mold with a 5.5-lbf (24.4-N)
rammer dropped from a height of 12 in. (305 mm) producing a compactive effort of 12,400
ft-lbf/ft3(600 kN-m/m3).
These test methods apply only to soils (materials) that have 30 % or less by mass of
particles retained on the 3∕4-inch (19.0-mm) sieve.
Three alternative methods are provided. The method used shall be as indicated in the
specification for the material being tested. If no method is specified, the choice should be
based on the material gradation.
Standard Reference:
ASTM Standards: ASTM D 698
Table 1 Alternative Proctor Test Methods
Modified Proctor
Standard Proctor
ASTM 698
ASTM 1557
Method A Method B Method C Method A Method B Method C
Material
>20%
Retained
on
No.3/8”
<30%
Retained
on
3/4” Sieve
3/8” Sieve
≤ 20%
Retained
on
No.4 Sieve
>20%
Retained
on
No.4
≤ 20%
Retained
on
3/8” Sieve
>20%
Retained
on
No.3/8”
<30%
Retained
on
3/4” Sieve
3/4” Sieve
Sieve No.4
3/8” Sieve
3/4” Sieve
4” DIA
6” DIA
4” DIA
4” DIA
6” DIA
3
3
3
5
5
5
25
25
56
25
25
56
≤ 20%
Retained
on
No.4 Sieve
For test
sample, use Sieve No.4
soil passing
4” DIA
Mold
No. of
Layers
No. of
blows/layer
>20%
Retained
on
No.4
≤ 20%
Retained
on
3/8” Sieve
Note: Volume of 4” diameter mold = 944 cm3 , Volume of 6” diameter mold = 2123 cm3
(verify these values prior to testing)
Significance and Use
Soil placed as engineering fill (embankments, foundation pads, road bases) is compacted to a
dense state to obtain satisfactory engineering properties such as, shear strength,
compressibility, or permeability. Also, foundation soils are often compacted to improve their
engineering properties. Laboratory compaction tests provide the basis for determining the
percent compaction and water content needed to achieve the required engineering properties,
and for controlling construction to assure that the required compaction and water contents are
achieved.
Summary of Test Method
A soil at a selected water content is placed in three layers into a mold of given dimensions,
with each layer compacted by 25 or 56 blows of a 5.5-lbf (24.4-N) rammer dropped from a
distance of 12-in. (305-mm), subjecting the soil to a total compactive effort of about 12,400
ft-lbf/ft3 (600kN-m/m3). The resulting dry unit weight is determined. The procedure is
repeated for a sufficient number of water contents to establish a relationship between the dry
unit weight and the water content for the soil. This data, when plotted, represents a
curvilinear relationship known as the compaction curve. The values of optimum water
content and standard maximum dry unit weight are determined from the compaction curve.
Apparatus
1 Mold Assembly :(Mold, 4 in. or Mold, 6 in.)
2 Sample Extruder
3 Balance
4 Drying Oven
5 Straightedge
6 Sieves —3∕4 in. (19.0 mm), 3∕8 in. (9.5 mm), and No. 4 (4.75 mm)
7 Mixing Tools —Miscellaneous tools such as mixing pan, spoon, trowel, spatula,
etc., or a suitable mechanical device for thoroughly mixing the sample of soil with
increments of water.
Test Sample
1 The required sample mass for Methods A and B is approximately (16kg), and for Method C
is approximately (29kg) of dry soil. Therefore, the field sample should have a moist mass of
at least (23kg) and (45kg), respectively.
2 Determine the percentage of material (by mass) retained on the No. 4 (4.75mm), 3∕8in.
(9.5mm), or 3∕4in. (19.0mm) sieve as appropriate for choosing Method A, B, or C. Make this
determination by separating out a representative portion from the total sample and
determining the percentages passing the sieves of interest by Test Methods D 422 or Method
C 136. It is only necessary to calculate percentages for the sieve or sieves for which
information is desired.
Test Procedure:
1. Break up the dry soil sample until approximately 3,000 g passes a 4.75 mm (No. 4) sieve.
2. Determine and record the dry mass of the soil sample (M).
3. Compute the mass of water (Mw) to be added to obtain the following cumulative moisture
contents (w): w = 7, 9, 11, 13, and 15 percent
4. Determine and record the mass of the mould (Mm) (without the collar).
5. Add seven (7) percent water to the dry soil and mix thoroughly.
6. Attach the collar to the mould and form a specimen by compacting the prepared soil in
three
equal layers to give a total compacted depth of about twelve (12) cm. Compact each layer by
imparting 25 evenly distributed blows from the hammer dropping from a height of 305 mm
(12 in.) above the soil. During compaction, the mould should rest on a uniform rigid base.
7. Remove the collar and trim the excess soil extending above the mould with a straightedge.
Determine and record the mass of the moist soil plus mould (M + Mm).
8. Subtract the weight of the mould and compute the (bulk) unit weight.
W
V
9. Remove the soil from the mould, cut the specimen vertically through the centre and take a
sample for a moisture content determination from one of the cut faces. Weigh this sample
IMMEDIATELY and place in the oven for 24 hours at 110 C.
10. Return the specimen to the remainder of the sample and break up the material until it will
pass a 4.75 mm (No. 4) sieve. (It is not necessary to actually pass the material through the
sieve; use your judgment).
11. Add water to increase the moisture content to the next cumulative moisture content
(Step3)
and mix the sample thoroughly.
NOTE: The amount of dry soil will decrease each time a sample is taken for a moisture
content determination. However, for the purpose of Step 3 calculations assume that the dry
mass (Ms in Step 2) is constant.
12. Repeat the procedure (Step 6) until there is either a decrease or no change in the unit
weight.
13. Calculate (the next day) the moisture content and the dry unit weight for each compacted
soil trial using
where γd is the dry unit weight.
1
w
Results
To complete the lab
• Finish filling out the data sheet
• Plot dry unit weight vs moisture content curve along with the 80 and 100 percent saturation
curves using
1
.
.
where S is degree of water saturation in decimal format and Gs is specific gravity of solids.
• Determine the optimum moisture content and dry unit weight
• Plot the total unit weight curve vs moisture content
• Answer the following questions.
1. Comment on the differences between the bulk unit weight and dry unit weight versus
moisture content plots and describe why they are different.
2. Contract specifications require a relative compaction of at least 95 percent standard
Proctor. To achieve these specifications, what field moisture content and dry unit weight
does the contractor require?
3. Why is soil compaction an important part of earthwork construction in engineering
earthworks?
4. Why do most geotechnical engineers specify greater compactive effort than the standard
Proctor test?
5. Assume that a modified Proctor was performed instead of the standard Proctor. Comment
on expected values of optimum moisture content and maximum dry unit weight.
6. Why does maximum dry unit weight decrease at water contents greater than optimum?
EXPERIMENT 6
CALIFORNIA BEARING RATIO TEST
PURPOSE:
To determine the California bearing ratio by conducting a load penetration test in the
laboratory.
SIGNIFICANCE:
The California bearing ratio test is penetration test meant for the evaluation of subgrade
strength of roads and pavements. The results obtained by these tests are used with the
empirical curves to determine the thickness of pavement and its component layers. This is the
most widely used method for the design of flexible pavement.
This instruction sheet covers the laboratory method for the determination of C.B.R. of
undisturbed and remoulded /compacted soil specimens, both in soaked as well as unsoaked
state.
EQUIPMENT
1. Cylindrical mould with inside diameter 152,4 mm and height 177,8 mm, provided with a
detachable extension collar 50,8 mm height and a detachable perforated base plate 10 mm
thick.
2. Spacer disc 150,8 mm in diameter and 61,37 mm in height along with handle.
3. Metal rammers. Weight 2.6 kg with a drop of 310 mm (or) weight 4.89 kg a drop 450
mm.
4. Weights. One or two annular metal weights having a total mass of 4.54 kg and slotted
metal weights each having masses of 2.27 kg. The annular weight shall be (149.23 to 150.81
mm) in diameter and shall have a center hole of approximately 21∕8in. (53.98 mm).
5. Loading machine. With a capacity of at least 5000 kg and equipped with a movable head
or base that travels at an uniform rate of 1.27 mm/min. Complete with load indicating
device.
6. Metal penetration piston 50 mm diameter and minimum of 100 mm in length.
7. Two dial gauges reading to 0.01 mm.
8. Sieves. 4.75 mm and 19 mm Sieves.
9. Miscellaneous apparatus, such as a mixing bowl, straight edge, scales soaking tank or pan,
drying oven, filter paper and containers
.
DEFINITION OF C.B.R.
It is the ratio of force per unit area required to penetrate a soil mass with standard circular
piston at the rate of 1.27 mm/min. to that required for the corresponding penetration of a
standard material.
C.B.R. = Test load/Standard load x 100
The following table gives the standard loads adopted for different penetrations for the
standard material with a C.B.R. value of 100%. The test may be performed on undisturbed
specimens and on remoulded specimens which may be compacted either statically or
dynamically.
PREPARATION OF TEST SPECIMEN
Undisturbed specimen
Attach the cutting edge to the mould and push it gently into the ground. Remove the soil
from the outside of the mould which is pushed in . When the mould is full of soil, remove it
from weighing the soil with the mould or by any field method near the spot.
Determination of the density
Remoulded specimen
Prepare the remoulded specimen at Proctors maximum dry density or any other density at
which C.B.R is required. Maintain the specimen at optimum moisture content or the field
moisture as required. The material used should pass 19 mm sieve but it should be retained on
4.75 mm sieve. Prepare the specimen either by dynamic compaction or by static compaction.
Dynamic Compaction
Take about 6 kg of soil and mix thoroughly with the required water.
Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base.
Place the filter paper on the top of the spacer disc.
Compact the mix soil in the mould using either light compaction or heavy compaction. For
light compaction, compact the soil in 3 equal layers, each layer being given 55 blows by the
2.6 kg rammer. For heavy compaction compact the soil in 5 layers, 56 blows to each layer by
the 4.89 kg rammer.
Remove the collar and trim off soil.
Turn the mould upside down and remove the base plate and the displacer disc.
Weigh the mould with compacted soil and determine the bulk density and dry density.
Put filter paper on the top of the compacted soil (collar side) and clamp the perforated base
plate on to it.
Static compaction
Calculate the weight of the wet soil at the required water content to give the desired density
when occupying the standard specimen volume in the mould from the expression.
W =desired dry density * (1+w) V
Where W = Weight of the wet soil
w = desired water content
V = volume of the specimen in the mould (as per the mould available in laboratory)
Take the weight W (calculated as above) of the mix soil and place it in the mould.
Place a filter paper and the displacer disc on the top of soil.
Keep the mould assembly in static loading frame and compact by pressing the displacer disc
till the level of disc reaches the top of the mould.
Keep the load for some time and then release the load. Remove the displacer disc.
The test may be conducted for both soaked as well as unsoaked conditions.
If the sample is to be soaked, in both cases of compaction, put a filter paper on the top of the
soil and place the adjustable stem and perforated plate on the top of filter paper.
Put annular weights to produce a surcharge equal to weight of base material and pavement
expected in actual construction. Each 2.27 kg weight is equivalent to 7 cm construction. A
minimum of two weights should be put.
Immerse the mould assembly and weights in a tank of water and soak it for 96 hours.
Remove the mould from tank.
Note the consolidation of the specimen.
Procedure for Penetration Test
Place the mould assembly with the surcharge weights on the penetration test machine.
Seat the penetration piston at the center of the specimen with the smallest possible load, but
in no case in excess of 4 kg so that full contact of the piston on the sample is established.
Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the
penetration rate is about 1.27 mm/min.
Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10 and
12.5 mm. Note the maximum load and corresponding penetration if it occurs for a
penetration less than 12.5 mm.
Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3
cm layer and determine the moisture content.
Observation and Recording
For Dynamic Compaction
Optimum water content (%)
Weight of mould + compacted specimen g
Weight of empty mould g
Weight of compacted specimen g
Volume of specimen cm3
Bulk density g/cc
Dry density g/cc
For static compaction
Dry density g/cc
Moulding water content %
Wet weight of the compacted soil, (W)g
Period of soaking 96 hrs. (4days).
For penetration Test
If the initial portion of the curve is concave upwards, apply correction by drawing a tangent
to the curve at the point of greatest slope and shift the origin. Find and record the correct load
reading corresponding to each penetration.
C.B.R. = PT/PS x 100
where PT = Corrected test load corresponding to the chosen penetration from the load
penetration curve.
PS = Standard load for the same penetration taken from the table.
Interpretation and recording
C.B.R. of specimen at 2.5 mm penetration
C.B.R. of specimen at 5.0 mm penetration
C.B.R. of specimen at 2.5 mm penetration
The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the
C.B.R. value at 2.5 mm will be greater that at 5 mm and in such a case/the former shall be
taken as C.B.R. for design purpose. If C.B.R. for 5 mm exceeds that for 2.5 mm, the test
should be repeated. If identical results follow, the C.B.R. corresponding to 5 mm penetration
should be taken for design.
EXPERIMENT 7
INSITU SOIL DENSITY BY THE SAND CONE METHOD
Purpose:
This method covers the determination of the in-place density of compacted soil or soilaggregate mixtures. The in-place dry density is expressed as a percentage of the soils
maximum dry density and can be compared to specification requirements.
Standard Reference:
Standard: AASHTO T 191
Theory
Density is defined as the mass per unit volume of soil
=
W
V
Where = mass density of soil
w = total mass of soil
v = total volume of soil
Here mass and volume of soil comprise the whole soil mass. In the above figure,
voids may be filled with both water and air or only air or only water, consequently the soil
may be wet or dry or saturated. In soil the mass of air is consider negligible and therefore the
saturated density is maximum , dry density is minimum and wet density is in between the
two if soils are found below water table submerged density is also estimated. The density can
be expressed in g/cm3, or t/m3 or kg/m3 or 1b/t3. For calculating the submerged density the
density of water is taken as 1 g/c3 = 1 t/m3
Dry density of the soil is calculated by using equation
 d=
Where,
d
= dry density of soil
t = wet density of soil
t
1+w
w = moisture content of soil
Density of soil may be determined by core cutter test, sand replacement method and
gamma ray method. Void ratio (e) is the ratio of volume of voids to volume of soil solids.
Degree of saturation (S) is defined as the ratio of volume of water to volume of voids.
e=
Vv
X100
S=
Vs
Vw
Vv
X100
Where e = voids ratio in %
S = degree of saturation in %
VV = Volume of voids
Vs= Volume of solids
Vw= Volume of water
Further, the following relationships can be obtained
e=
Gs w
d
-1
S=
Gs w
e
Where Gs = specific gravity of soil solids
d = dry density
w = density of water
w = water content
EQUIPMENT
Sand density apparatus and base plate Clean, free-flowing sand consisting of No.10 +No.200
Balance, readable to 0.1 grams
Pins, shovel, trowel, spoon, hammer, and knife Auger, 4" diameter, Sealable container
PREPARATION
Filling the apparatus
1. Place the empty apparatus upright on a firm level surface, close the valve and fill the
funnel with sand.
2. Open the valve and keep the funnel at least half full with sand during filling. When the
sand stops flowing into the apparatus, close the valve sharply and empty the excess sand.
3. Determine and record the mass of the apparatus filled with sand (m1).
Determining the mass of sand required to fill the funnel and base plate (Cone
Correction)
1. Place the base plate on a clean, level, plane surface. Invert the sand cone filled with sand,
and seat the funnel in the recess of the base plate.
2. Open the valve fully and allow the sand to flow until the sand stops flowing.
3. Close the valve sharply, remove the apparatus, and determine the mass of the apparatus
and the remaining sand (m2).
4. The mass of sand required to fill the cone and base plate is calculated by the difference
between the initial mass and final mass. Record this mass as the cone correction: (Cc = m1 –
m2).
Where:
CC = Cone correction
m1 = Mass of the apparatus filled with sand
m2 = Mass of the apparatus and remaining sand
Determining the bulk density of sand ( B)
Determine the bulk density of the calibration sand (sand calibration factor). Divide the mass
of the sand needed to fill the container, by the volume of the calibration container.
B =mB/VB
Where:
DB = Bulk density of the sand in g/cm3
mB = Mass of sand
VB = Volume of the calibration container
PROCEDURE
Fill testing apparatus with sand and record the total mass.
Select the area of compacted lift to be tested. Because the surface of a compacted area is
generally loose or disturbed due to compaction operations, remove loose material and level
off an area slightly larger than the base plate.
Place the base plate over the smoothed area and fasten down with the accompanying pins.
Plate must stay in this position and be stable throughout the test.
Dig a test hole within base plate opening, with the auger, trowel, or other tools.
Soils that are granular require extreme care and may require the digging of a conical-shaped
hole. Place all of the loosened material from the hole into an aggregate balance pan, or a
moisture-tight container if not weighed right away.
Minimum Test Hole Volumes and Moisture Content Samples Based on Maximum Size
Maximum
Particle Size
No. 4 (4.75 mm)
1/2" (12.5 mm)
1" (25.0 mm)
2" (50.0 mm)
Minimum Test Hole
Volume (cm3)
700
1400
2100
2800
Minimum Sample Size
for Moisture Content
100 g
250 g
500 g
1000 g
CALCULATIONS
Complete calculations as follows:
• (VH) Volume of Test Hole = (Initial Mass - Final Mass - CC)/ B
• (mS) Dry Mass of Material removed from test hole = (Moist Mass removed from test hole/
(1 + (% moisture /100))
• ( D) Dry Density = mS/VH
CALIBRATION
All new devices should be calibrated prior to being used. A calibration check should be
performed annually as a minimum, or whenever damage or repair occurs.
EXPERIMENT 8
PERMEABILITY TEST
(CONSTANT HEAD AND FALLING HEAD)
A. CONSTANT HEAD (standard ASTM D 2434)
Purpose
Determine the coefficient of permeability of coarse soils.
In this test, water is forced by a known constant pressure through a soil specimen of known
dimensions and the rate of flow is determined. This test is used primarily to determine the
suitability of sands and gravels for drainage purposes, and is made only on remolded
samples.
Standard Reference:
ASTM Standards: ASTM D 2434
EQUIPMENT
1. Permeameter mould of non-corrodible material having a capacity of 1000 ml, with an
internal diameter of 100 mm and internal effective height of 127.3 mm.
2. The mould shall be fitted with a detachable base plate and removable extension counter.
3. Compacting equipment: 50 mm diameter circular face, weight 2.76 kg and height of fall
310 mm.
4. Constant head tank: A suitable water reservoir capable of supplying water to the
permeameter under constant head.
5. Graduated glass cylinder to receive the discharge.
6. Stop watch to note the time.
7. A meter scale to measure the head differences and length of specimen.
PREPARATION OF SPECIMEN FOR TESTING
1- The specimen consists of a representative portion of the sample under consideration
from which all aggregate retained on the 19-mm sieve has been removed.
2- Compaction of test specimens:
a) Add water to bring the test specimen to slightly below the apparent optimum
moisture content, or sufficient water to assure good compaction. Mix the water
and material thoroughly with the aid of the soil mixer
b) Compact the wetted specimen in the mold with solid base plate attached, in three
equal layers, Each layer receives 25 Blows with hammer. Scarify each compacted
layer before adding the next layer.
c) Place the perforated plate on the specimen and close the mold
TEST PROCEDURE
1. For the constant head arrangement, the specimen shall be connected through the top inlet
to the constant head reservoir.
2. Open the bottom outlet.
3. Establish steady flow of water.
4. The quantity of flow for a convenient time interval may be collected.
5. Repeat three times for the same interval.
OBSERVATION AND RECORDING
The flow is very low at the beginning, gradually increases and then stands constant. Constant
head permeability test is suitable for cohesion less soils. For cohesive soils falling head
method is suitable.
COMPUTATION
Coefficient of permeability for a constant head test is given by
Details of sample
Diameter of specimen
……… cm
Length of specimen(L)
……… cm
Area of specimen (A)
……… cm2
Specific gravity of soil Gs
……….
Volume of specimen (V)
………. cm3
Weight of dry specimen (Ws) ………g
Moisture content
……….%
Experiment No.
1
Length of specimen
L(cm)
Area of specimen
A(cm2)
Time t
(sec)
Discharge
q(cm3)
Height of water
h(cm)
Temperature
(o C)
Interpretation and Reporting
2
3
B- FALLING HEAD
PURPOSE
In this test, water is forced, by a falling head pressure, through a soil specimen of known
dimensions and the rate of flow is determined. This test is used to determine the drainage
characteristics of relatively fine-grained soils and is usually performed on undisturbed
samples.
APPARATUS
1. This test utilizes the same apparatus as an earlier consolidation test with slight
modifications.
2. An “O” ring seal is provided to force the water to move through the soil rather than around
the outside of the ring.
PREPARATION OF SAMPLE
1. The soil samples are received in the laboratory in the 50.8 mm diameter by 101.6mm long
brass tubes, or in larger containers from which specimens must be trimmed.
2. The 50.8 mm by 101.6 mm tubes are relatively thin-walled and flexible; therefore, handle
them with care so that the soil is not deformed inside the tube.
3. Extrude the soil from the sample tube into the 25.4 mm high consolidometer rings
(sampler tubing) by pushing the piston into the sample tube. This extrusion should move the
sample in the same direction with reference to the tube as it moved during the sampling
operation in order to minimize disturbance of the soil structure.
4. Select a good specimens and trim carefully to the exact height of the ring by means of a
fine wire . Exercise care in these operations so as to disturb the sample as little as possible
and to maintain a tight fit of the specimen in the ring. Do all the work swiftly to prevent
excessive drying of the soil.
TESTING PROCEDURE
The specimen cannot be placed with the apparatus tipped on its side as the apparatus must be
filled with water at all times. The placing procedure requires the following steps:
1. Place soil ring and specimen with “O” ring, on bottom porous stone.
2. Slide consolidometer over soil ring, place upper plate and fasten securely to the base with
3 nuts to ensure “O” ring seal.
3. Insert top porous stone and piston which applies a 6.0 kPa pressure on the specimen.
Record initial dial reading to determine subsequent change in specimen height, for unit
weight calculations, due to increasing load increments.
4. Bleed air out of the system by allowing water to flow from the reservoir across the bottom
porous stone and also through the conduit system. It is imperative that all air bubbles be
flushed out of the system. Close the bleeding valve in the base of apparatus.
5. Record initial dial reading, then apply the load. Record final dial reading.
6 .Fill standpipe. Record the height of water in the tube.
7 .Release the quick-acting flow valve and the test is in progress.
8. Record time in seconds for head of water to fall to the level of the overflow pipe.
9. Repeat steps 6 through 8 several times to establish an average permeability for each load
increment used.
5. CALCULATIONS
Compute the coefficient of permeability from the following formula:
K =RT. 2.3 (aL/At) log10 (h1/h2)
Where:
K = coefficient of permeability.
RT=Correction coefficient.
a = cross-sectional area of the standpipe.
L = average height of the sample for the load increment.
A = cross-sectional area of the sample.
t = elapsed time increment.
h1 = height of water at the beginning of time increment in millimeters .
h2 = height of water at the end of time increment in millimeters .
EXPERIMENT 9
CONSOLIDATION TEST
Purpose:
This test is performed to determine the magnitude and rate of volume decrease that a laterally
confined soil specimen undergoes when subjected to different vertical pressures. From the
measured data, the consolidation curve (pressure-void ratio relationship) can be plotted. This
data is useful in determining the compression index, the recompression index and the
preconsolidation pressure (or maximum past pressure) of the soi. In addition, the data
obtained can also be used to determine the coefficient of consolidation and the coefficient of
secondary compression of the soil.
Standard Reference:
ASTM Standards: ASTM D 2435
Significance:
The consolidation properties determined from the consolidation test are used to estimate the
magnitude and the rate of both primary and secondary consolidation settlement of a structure
or an earthfill. Estimates of this type are of key importance in the design of engineered
structures and the evaluation of their performance.
Equipment:
Consolidation device (including ring, porous stones, water reservoir, and load plate), Dial
gauge (…..), Sample trimming device, glass plate, Metal straight edge, Clock, Moisture can,
Filter paper.
1- Consolidation frame
2- Consolidation cell
3- Displacement transducer
4- Loading yoke
5- Counter balance weight
6- Beam
7- Beam support jack
8- Weight hanger
Test Procedure:
1 Determine the size and mass of the oedometer ring.
2. Assembly of the consolidation cell
- Place the cell body on the cell base
- Place the bottom porous disc on the cell base
- Put the cutting ring with specimen centrally in to the cell with its cutting edge uppermost.
- Fix the ring retainer around the ring, so that it is securely held, and tighten the clamping
screws
- Place the upper porous disc
- Place the loading cap centrally on top
3. Assemble the apparatus using filter papers between the soil and the porous stones, balance
the lever arm, and set the dial indicator to zero.
The usual procedure is to start with a small stress and to double the stress for each load
increment. Normal loadings will be 6.25, 12.5, 25, 50, 100, 200, and 400 kPa; then unload to
100, 25, and finally 6.25 kPa.
4. Add the first prescribed load to the hanger at the back of the machine and record dial
readings.
Measure with suitable intervals the vertical displacement; the following periods of elapsed
time from zero are convenient. 0, 10, 20, 30, 40, 50 s, 1, 2, 4, 8, 15, 30 min, 1, 2, 4, 8, 24
hours
Note: Compression is likely to be minimal and rapid under this first load. When insignificant
movement is occurring, fill the cell with distilled water that is at room temperature. If the
sample starts to swell, stop the test and add another increment of load.
5. Continue taking readings at the suggested times given on the data sheet for the first hour.
Allow the load to remain on the sample for 24 hours before applying the next load increment.
6. Following the load/unload sequence, allow the sample to swell for 24 hours at the final
load of 6.25 kPa. Remove it from the cell, blot surplus water, and determine the mass of the
ring plus sample.
7. Place both the ring and sample in an oven, dry, and obtain the mass of the dry soil plus
ring.
Analysis:
(1) Calculate the initial water content (wi (%)) and specific gravity of the soil (Gs).
(2) For each pressure increment, construct a semilog plot of the consolidation dial readings
versus the log time (in minutes). Determine D0, D50, D100, and the coefficient of
consolidation (cv) using Casagrande’s logarithm of time fitting method. See example data.
Also calculate the coefficient of secondary compression based on these plots.
(3) Calculate the void ratio at the end of primary consolidation for each pressure increment.
Plot log pressure versus void ratio. Based on this plot, calculate compression index,
recompression index and pre-consolidation pressure (maximum past pressure).
(4) Summarize and discuss the results.
EXPERIMENT 10
DIRECT SHEAR TEST
Purpose:
This test is performed to determine the consolidated-drained shear strength of a sandy to silty
soil. The shear strength is one of the most important engineering properties of a soil, because
it is required whenever a structure is dependent on the soil’s shearing resistance. The shear
strength is needed for engineering situations such as determining the stability of slopes or
cuts, finding the bearing capacity for foundations, and calculating the pressure exerted by a
soil on a retaining wall.
Standard Reference:
ASTM D 3080 - Standard Test Method for Direct Shear Test of Soils Under
Consolidated Drained Conditions
Significance:
The direct shear test is one of the oldest strength tests for soils. In this laboratory, a direct
shear device will be used to determine the shear strength of a cohesion less soil (i.e. angle of
internal friction (f)). From the plot of the shear stress versus the horizontal displacement, the
maximum shear stress is obtained for a specific vertical confining stress. After the
experiment is run several times for various vertical-confining stresses, a plot of the maxi
mum shear stresses versus the vertical (normal) confining stresses for each of the tests is
produced. From the plot, a straight-line approximation of the Mohr-Coulomb failure
envelope curve can be drawn, f may be determined, and, for cohesion less soils (c = 0), the
shear strength can be computed from the following equation:   tan
Equipment:
Direct shear device, Load and deformation dial gauges, Balance.
Figure: Principles of direct shear
Test Procedure:
(1) Weigh the initial mass of soil in the pan.
(2) Measure the diameter and height of the shear box. Compute 15% of the diameter in
millimeters.
(3) Carefully assemble the shear box and place it in the direct shear device. Then place a
porous stone and a filter paper in the shear box.
(4) Place the sand into the shear box and level off the top. Place a filter paper, a porous stone,
and a top plate (with ball) on top of the sand
(5) Remove the large alignment screws from the shear box! Open the gap between the shear
box halves to approximately 0.025 in. using the gap screws, and then back out the gap
screws.
(6) Weigh the pan of soil again and compute the mass of soil used.
(7) Complete the assembly of the direct shear device and initialize the three gauges
(Horizontal displacement gage, vertical displacement gage and shear load gage) to zero.
(8) Set the vertical load (or pressure) to a predetermined value, and then close bleeder valve
and apply the load to the soil specimen by raising the toggle switch.
(9) Start the motor with selected speed so that the rate of shearing is at a selected constant
rate, and take the horizontal displacement gauge, vertical displacement gage and shear load
gage readings. Record the readings on the data sheet. (Note: Record the vertical displacement
gage readings, if needed).
(10) Continue taking readings until the horizontal shear load peaks and then falls, or the
horizontal displacement reaches 15% of the diameter.
Analysis:
(1) Calculate the density of the soil sample from the mass of soil and volume of the shear
box.
(2) Convert the dial readings to the appropriate length and load units and enter the values on
the data sheet in the correct locations. Compute the sample area A, and the vertical (Normal)
stress
(3) Calculate shear stress
(4) Plot the horizontal shear stress versus horizontal (lateral) displacement
(5) Calculate the maximum shear stress for each test.
(6) Plot the value of the maximum shear stress versus the corresponding vertical stress for
each test, and determine the angle of internal friction from the slope of the approximated
Mohr-Coulomb failure envelope.