Comprehensive Soil Testing Techniques for Engineering Applications

SOIL TESTING TECHNIQUES
- Prepared by
Adarsh Sanjay Kudkelwar
Sr. Engineer - Planning

SCOPE OF TESTING
➢ Soil
✓ Grain Size Distribution
• Sieve Analysis
• Hydrometer Analysis
✓ Natural Moisture Content(NMC)/ Water Content
✓ Specific Gravity
✓ Bulk & Dry Density
✓ Liquid Limit, Plastic Limit and Plasticity Index
✓ Free Swell Index
✓ Triaxial Compressive Strength on undisturbed soil sample/ Unconsolidated Undrain Test
✓ Consolidation Test on undisturbed soil
➢ Rock
✓ Point Load Index of Rock
✓ Uniaxial Compressive Strength of rock
• Without Saturation
• With Saturation of 7 days

Grain Size Analysis
1. Sieve Analysis (IS 2720 Part 4)
Purpose: To determine the particle size distribution of a coarse-grained soil sample by passing it through a series of standard sieves.
Soil sample greater than 75 micron, the sieve analysis method is being used.
Soil sample less than 75 micron, the Pittete method is given as standard method while hydrometer analysis is given as subsidiary method.
Procedure:
1. Take about 500-1000 gm of soil sample and kept in oven for 24 hrs. at 105-110° C to make it dry.
2. Allow it to cool and measure the total dry weight.
3. Arrange the sieves in descending order of their size and keep pan at bottom of sieves.
4. Pour the dry soil sample into the top sieve and cover it with sieve stack.
5. Shake it for up to 10-15 minutes.
6. Remove each sieves carefully and the weight of sample retained on that sieves.
Apparatus: Standard IS Sieves, Sieve Shaker, Weighing machine, Oven, Tray/Pan
Calculation:
Percentage (%) Retained = ______________________________ X 100
Weight of soil sample retained
Total Weight of Sample
Cumulative (%) Retained = ______________________________ X 100
Cumulative Weight Retained
Total Weight of Sample
Percentage (%) Passing = 100 – Cumulative % Retained

Sieve Size (mm) Weight Retained
(g)
Cumulative Weight
Retained (g)
% Retained Cumulative %
Retained
% Passing
4.75 1 A=1 P=(1/total).100 X=P =100-X
0.425 2 B=A+2 Q=(2/total).100 Y=X+Q =100-Y
0.075 3 C=B+3 R=(3/total).100 Z=Y+R =100-Z
Observation Table: (Template table)
Sieve Size (mm) Weight Retained
(g)
Cumulative Weight
Retained (g)
% Retained Cumulative %
Retained
% Passing
4.75 40 40 20 20 80
0.425 120 160 60 80 20
0.075 30 190 15 95 5
Pan 10 200 5 100 0
For Example: (200 gm)

Determination of Gradation Coefficient:
Plot a graph on semi log graph paper based on calculated table;
X- axis: Particle Scale (mm)
Y- axis: % of soil passing
Mark the curve intersecting at 10%, 30% and 60%
Determination of D10,D30 and D60
D10 = Size of particle corresponding to 10% passing
Coefficient of Uniformity (Cu) = _______
D60
D10
Coefficient of Curvature (Cc) = ___________
𝐷30
2
D60 X D10
Standard Range:
• For Well graded Gravel: Cu ≥ 4, 1 ≤ Cc ≤ 3
• For Well graded Sand: Cu ≥ 6, 1 ≤ Cc ≤ 3
• Otherwise, soil is considered as poor graded soil.

Purpose: To determine the particle size distribution of the fine-grained fraction of soil (particles smaller than 75 μ) using a hydrometer based on Stoke’s law.
Apparatus: Hydrometer, Sedimentation Cylinder, Mechanical Stirrer, Weighing Machine, Thermometer, Stopwatch, Sieve (75 µ)
Chemicals: Sodium Hexametaphosphate, Distilled Water
Procedure: 1. Take about 50gm of oven dried soil sample passing through the 75 µ IS Sieve.
2. Add appr. 125 ml of sodium hexametaphosphate solution with the soil and mixed properly using mechanical stirrer.
3. Transfer all mixture into 1000 ml sedimentation cylinder and add distilled water into cylinder up to 1000 ml mark.
4. Mix it properly and place the cylinder on the table. Start stopwatch.
5. Take hydrometer reading at 30 secs, 1 min, 2 min, 4 min, 8 min, 15min, 30 min, 60 min, 120 min, 240 min, 24 hrs.
Observation Table:
Time (Min) Hydrometer Reading Corrected Reading (Rc)
Effective Length (L)
(cm)
Particle Diameter (mm) % Finer
0.5
1
2
4
8
15
30
60
120
240
1440 (24hrs)
Hydrometer Analysis

Calculation:
1. Corrected Hydrometer Reading
Rc = R + Cm + Ct − Cd
Where,
Rc = Observed hydrometer reading
Cm = Meniscus Correction
Ct = Temperature Correction
Cd = Dispersing Agent Correction
2. Effective Length
L = 16.3 – 0.164 R
Where,
L = Effective Length
R = Corrected Hydrometer Reading
3. Particle Diameter
d = 18𝑣𝐿 ÷ 𝑔 𝐺𝑠 − 1 𝑡
Where,
d = Particle Diameter (mm)
L= Effective Length (cm)
t= Time
Gs = Specific Gravity of Soil
v = Kinetic viscosity of water
4. % Finer
% Finer =
Where,
Rc = Observed Hydrometer Reading
W = Weight of oven dried soil sample
𝑅𝑐 𝑥 100
𝑊
Or d =
𝐿
𝑡

Water Content Analysis (IS 2720 Part 2)
Purpose: To determine the water (moisture) content of a soil sample by the oven-drying method.
Apparatus: Oven, Weighing machine, containers with lids
Procedure:
1. Clean the container, dry it and take a weigh with lid (M1).
2. Take a 25gm of soil sample passing through 425 IS sieve. Mixed with water and place in container, closed with lid. Take a weight (M2).
3. Keep the container (without lid) in an oven for 24 hours at temperature of 105-110°C ± 5°C.
4. Remove the container from oven and keep it with lid for natural cooling.
Observation 1 2 3
Mass of empty container (M1)
Mass of container + soil (M2)
Mass of container + dry soil (M3)
Observation Table:
Calculation:
Mass of water (Mw) = M2 – M3
Mass of solid (Ms) = M3 – M1
Water Content (w) = _____________________
Mass of water
Mass of solid
X 100

Specific Gravity (IS 2720 Part 3)
Purpose: To determine the specific gravity of a soil sample by the pycnometer method.
Apparatus: Pycnometer, Weighing machine, Oven, Distilled water, Thermometer
Procedure:
1. Clean and dry the pycnometer thoroughly with cap.
2. Weigh the empty pycnometer and record it (M1).
3. Take about 200-300 gm of oven dried soil sample into pycnometer and measure its weight (M2).
4. Add distilled water into it, close the cap and shake properly.
5. Fill the pycnometer with distilled water up to the mark and measure its weight (M3), record a temperature.
6. Now, empty the pycnometer, clean it and dry.
7. Fill the pycnometer with water only, close the cap and take a weight (M4).
Observation Table:
Calculation:
Specific Gravity (Gs) = _____________________________
M2 – M1
(W2 – W1) – (W3 – W4)
X 100
Observation 1 2 3
Room Temperature
Mass of Empty Pycnometer (M1)
Mass of pycnometer and dry soil (M2)
Mass of pycnometer, soil and water (M3)
Mass of pycnometer and water (M4)

Dry Density and Bulk Density
Purpose: To determine the bulk density and dry density of a soil sample by the core cutter method.
Apparatus: Core cutter with dolly, Rammer, Weighing machine, Oven, Water content containers, Vernier caliper
Procedure:
1. Measure the internal diameter and height of core cutter. (D = 100 mm, H = 130 mm)
2. Take a weight of empty core cutter (M1).
3. Clear and level the area about 300 sq. mm where test is carried out.
4. Place a dolly over the top of core cutter and press the core cutter into the soil by using rammer.
5. Stop the process of pressing when about 15 mm of the dolly protrudes above the soil surface.
6. Remove the soil surrounding to the core cutter and take core cutter out of ground.
7. Remove the dolly from core cutter. Trim top and bottom surface of core cutter carefully.
8. Measure the weight of core cutter filled with soil mass (M2).
9. Remove soil sample from core cutter, take some sample for water content determination.
10. Determine the water content of soil sample by using oven drying method.
Observation Table:
Observation 1 2 3
Internal Diameter (mm) 100 100 100
Height (mm) 130 130 130
Mass of empty core cutter (M1)
Mass of core cutter with soil (M2)
Calculation:
Mass of wet soil (M) = M2 - M1
Volume of Cutter (V) = _________
πd2 .H
4
Bulk Density (ϒ) = _________
V
M
Dry Density (ϒd) = _________
1 + w
ϒ
Core Cutter
Dolly
Rammer

Atterberg’s Limit of Soil (IS 2720 Part 5)
The water content at which soil changes from one state to the other is known as consistency limit or Atterberg’s limit.
Solid State Semi - Solid State Plastic State Liquid State
Water Content
Volume

Liquid Limit
Purpose: To determine the water content at which soil changes from liquid state to plastic state.
Apparatus: Casagrande apparatus, Grooving tool, Mixing dish, Spatula, Weighing machine, Oven
Procedures:
1. Take 120-150 gm of air-dried soil sample passing through 425µ IS sieve.
2. Add distilled water in soil and mixed it properly to form smooth and uniform paste.
3. Fill the soil paste into brass cup of Casagrande apparatus up to 10 mm depth from the center of cup, and level the surface.
4. With the help of the grooving tool, divide the soil paste in the cup along the diameter of the cup (through the center line of the cam follower) to get a clean, sharp groove
of proper dimensions.
5. Turn the handle of the apparatus at a rate of 2 revolutions per second until the two parts of the soil paste come in contact at the bottom of the groove and record the
number of revolutions to achieve this.
6. Collect the soil sample from apparatus in the container and kept in oven for determining the water content.
7. Plot a "flow curve" on a semi-log sheet with water content on y-axis (arithmetic scale) and number of blows on x-axis (log scale). Draw a well-defined straight line through
the points.
8. Record the moisture content corresponding to 25 blows and round off to the nearest whole number and report it as the liquid limit of the soil.

Observation Table:
Determination No. 1 2 3 4 5
Number of Blows
Container No.
Mass of [Container + Wet Soil] (gm)
Mass of [Container + Dry Soil] (gm)
Mass of Water (gm)
Mass of Container (gm)
Mass of Dry Soil (gm)
Moisture Content [WL] (%)
Calculation:
Water Content (WL) =
Wwet - Wdry
Wdry
___________ X 100

Plastic Limit
Purpose: To determine the water content at which soil stops behaving as a plastic material.
Apparatus: Flat glass plate, Spatula, weighing machine, Oven, air tight containers, distilled water,
Procedures:
1. Take soil sample of 20 gm, passing through 425µ IS sieve. Mix it on the glass plate with sufficient distilled water to make it plastic form.
2. Take about 8 gm of plastic form of soil , make a ball and roll it on glass with hands. Make it thread of uniform diameter throughout its length.
3. When a diameter of thread reached 3 mm, kneed the soil together to a uniform mass and once again roll it. Continue the process until the soil thread just crumbles at
3mm diameter.
4. Collect the crumbled soil threads in a container and determine the corresponding water content by oven drying method.
5. Repeat process up to three trials. Report the average water content rounded off to the nearest whole number as the plastic limit of the soil.
Determination No. 1 2 3
Container No.
Mass of [container + wet soil] (gm)
Mass of [container + dry soil] (gm)
Mass of water (gm)
Mass of container (gm)
Mass of dry soil (gm)
Water Content (WP)
Observation Table:
Plasticity Index (IP) = WL - WP

Free Swell Index (IS 2720 Part 40)
Purpose: To determine the free swell index of soil sample.
Apparatus: Oven, Weighing machine, 2 x 1000 mL graduated cylinder, Glass Rod, 425µ IS Sieve
Chemicals: Kerosine, Distilled Water
Procedures:
1. Take 10 gm of oven dried soil sample passing through 425µ IS sieve.
2. Divide soil sample into two portion i.e. 5 gm each.
3. Take 100 mL of distilled water into one graduated cylinder and 100 mL of kerosene into another graduated cylinder.
4. Add 5 gm of soil sample into distilled water cylinder and another 5 gm into kerosene.
5. Stir gently with glass rod to remove entrapped air.
6. Keep both cylinder for 24 hrs. in undisturbed condition to settle the soil.
7. Record the volume after 24 hrs.
Calculation:
Free Swell Index (FSL) =
Vw - Vk
Vk
_________ X 100
Where,
Vw= Volume of soil in Water (mL)
Vk= Volume of soil in Kerosene (mL)
Observation Table:
Sample No.
Weight of sample
(g)
Volume in water
(mL)
Volume in
kerosene (mL)
Free Swell Index
(%)
1
2
Interpretation:
Free Swell Index (%) Degree of Expansiveness
0 - 20 Low
20 – 35 Moderate
35 – 50 High
> 50 Very High

Unconfined Compressive Strength (IS 2720 Part 10)
Purpose: To determine the Unconfined Compressive Strength (UCS) of an undisturbed cohesive soil sample.
Apparatus: UCS Machine, Weighing machine, vernier caliper, dial gauge, sample trimming tool
Procedures:
1. Prepare a soil specimen at a desired water content and density in a large mould.
2. Push the sampling tube into large mould, and remove the sampling tube filled with the soil. For undisturbed samples, push the sampling tube into the clay sample.
3. Saturate the soil sample in the sampling tube by a suitable method.
4. Coat the split mould lightly with a thin layer of grease. Weigh the mould.
5. Extrude the sample out of the sampling tube into the split mould, using the sample extractor and the knife.
6. Trim the two ends of specimen in the split mould. Weigh the mould with the specimen.
7. Remove the specimen from the split mould by splitting the mould into two parts.
8. Measure the length and diameter of the specimen by using vernier caliper.
9. Place the specimen on the bottom plate of compression machine. Adjust the dial gauge and proving-ring gauge to zero.
10. Adjust the dial gauge and provide the ring gauge to zero.
11. Apply compression load to cause an axial strain at the rate of ½ to 2% per minute.
12. Record the dial gauge reading, and the providing ring reading every thirty seconds up to a strain of 6%. The reading may be taken after every 60 seconds for a strain
between 6% to 12%, and every 2 minutes or so beyond 12%.
13. Continue the test until failure surfaces have clearly developed or until an axial strain of 20% is reached.
14. Measure the angle between the failure surface and the horizontal, if possible.
15. Take the sample from the failure zone of the specimen for the water content determination.
Datasheet:
Initial length of specimen (L0) =
Initial area of specimen (A0) =
Mass of empty split mould =
Mass of specimen (M) =
Water Content (w) =
Specific Gravity (G) =
Initial diameter of specimen (D0) =
Initial volume of specimen (V0) =
Mass of split mould + specimen =
Bulk density (ρ) = M/V0
Dry density (ρ𝑑) =
Specific Gravity (G) =
Degree of saturation (S) = Void ratio (e) = _______
_______
w . G
- 1
G . 𝜌𝑤
X 100
e 𝜌𝑑

Sr No.
Observation Calculations
Elapsed Time
Dial Gauge Providing Ring Strain,
ε = ΔL / L0
Corrected Area,
A = A0 / (1 - ε)
Compressive Stress,
σ = P / A
Reading Deformation (ΔL) Reading Load (P)
1
2
3
Observation Table:
Calculations:
Shear Stress, S = qu / 2
Plot a curve between the compressive stress as ordinate and axial strain, as abscissa.
From the graph, unconfined compressive strength (qu) =

Consolidation Test on Undisturbed Soil (IS 2720 Part 15)
Purpose: To determine the consolidation characteristics of an undisturbed cohesive soil, including:
Compression Index (Cc)
Coefficient of Consolidation (Cv)
Coefficient of Volume Compressibility (Mv)
Coefficient of Compressibility (av)
Apparatus: Consolidation apparatus (oedometer) with loading device, Consolidation rings, Porous stones, Weighing machine, soil trimming tool, Water reservoir, Dial
gauge, water content can, oven
Procedures:
1. Clean and dry the meta ring. Measure its diameter and height. Take the mass of the empty ring.
2. Press the ring into the soil sample contained in a large container at the desired density and the water content. The ring is to be pressed with hands.
3. Remove the soil around the ring. The soil specimen should project about 10 mm on either side of the ring. Any voids in the specimen due to the removal of large size
particles should be filled back by pressing the soil lightly.
4. Trim the specimen flush with the top and bottom of the ring.
5. Remove any soil particles sticking to the outside of the ring. Weigh the ring with the specimen.
6. Take a small quantity of soil removed during trimming for the water content determination.
7. Saturate the porous stones by boiling them in distilled water for about 15 minutes.
8. Assemble the oedometer. Place he bottom porous stones, bottom filter paper, specimen, top filter and top porous stone.
9. Position the loading block centrally on the top porous stone. Mount the mould assembly on loading frame. Centre it such that the load applied is axial.
10. Set the dial gauge in position. Allow sufficient margin for the swelling of the soil.
11. Connect the mould assembly to the water reservoir having the water level at about the same level as the soil specimen. Allow the water to flow into the specimen
till it is fully saturated.
12. Take the initial reading of the dial gauge.
13. Apply an initial setting load to give a pressure of 5 kN/m2 (2.5 kN/m2 for very soft soils) to the assembly so that there is no swelling. Allow the setting load to stand
till there is no change in the dial gauge reading or for 24 hours.
14. Take a final gauge reading under the initial setting load.
15. Apply the first load increment to apply a pressure of 10 kN/m2, and start the stop watch. Record the dial gauge readings at 0, 0.25, 1.0, 2.25, 4.0, 6.25, 9.0, 12.25, 16,
20.25, 25, 36, 49, 60, 120, 240, 1440 (24 hrs) minutes.
16. Repeat the process for each load increment. (25, 50, 100, 200, 400, 800 kN)
17. After reaching the maximum load, unload the specimen in stages and record rebound readings.
18. Determine the moisture content after completion of the test by oven drying method.

Observation Table:
Load (kN) Dial Gauge Reading (mm)
5
10
25
50
100
200
400
800
Calculation:
Compression Index (Cc) =
(using e-log P curve)
___________
(Using Taylor's square-root-of-time
method)
Coefficient of Consolidation (Cv) =
Log(P2/P1)
e1 - e2
____________
t90
0.848 Hd
2
Where,
Hd = drainage path
T90 = time for 90% consolidation
Coefficient of Volume Compressibility (Mv) = _____
Δσ
ε
Coefficient of Compressibility (Mv) = Mv (1 + e0)

For Example: Graph
Casagrande’s Method Taylor’s Method

Point Load Index of Rock
Purpose: To determine the Point Load Strength Index (Is) of a rock specimen.
Apparatus: Point Load Testing Machine, Rock Sample, Vernier Caliper, Ruler, Weighing Machine
Procedures:
1. Select the rock specimen free from visible cracks.
2. Measure the dimension of rock specimen by using vernier caliper.
3. Calculate the equivalent diameter (De).
4. Place the rock sample in point load testing machine.
5. Apply the load gradually continuous up to specimen fails.
6. Record the maximum failure load (P).
7. Repeat the test of about 5 samples and calculate average value.
Observation Table:
Observation Value
Equivalent Diameter (De)
Height of Rock Sample (H)
Point Load (P)
Size Correction Factor (F)
Calculation:
As per recommendation of ISRM
Size Correction Factor (F) = (De/50)0.45 Point Load Strength Index (Is) = _______
Corrected Point Load Index (Is)50 = F x Is
De
2
P

Uniaxial Compressive Strength of Rock
Purpose: To determine the Uniaxial Compressive Strength (UCS) of rock specimens under:
1. Dry (without saturation) condition
2. Saturated condition (after 7 days of water saturation)
Apparatus: Compressive Testing Machine (CTM / UCS Machine), Vernier Caliper, Rock specimen, Weighing Machine, Water tank, Oven, Ruler
Procedures:
1. Prepare the rock sample with smooth, parallel ends.
2. Measure the length and diameter of specimen.
3. Dry the sample in an oven at 105 ± 5°C. Cool the specimen at a room temperature.
4. Place the rock specimen centrally between the loading plates of CTM.
5. Apply axial load continuously at a specified loading rate until its failure.
6. Record the maximum failure load.
1. Dry (Without saturation) Condition
Observation Table:
Observation Value
Diameter (D)
Length (L)
Maximum Load (P)
Calculation:
Cross Sectional Area (A) = ______
πd2
4
UCS = ______
P
A

Procedures:
1. Prepare the rock sample with smooth, parallel ends.
2. Measure the length and diameter of specimen.
3. Immerse the specimen in clean water for 7 days to ensure full saturation.
4. Remove specimen after 7 days, and wipe off surface with damp cloth.
5. Measure the dimension of specimen again.
6. Place the rock specimen centrally between the loading plates of CTM.
7. Apply axial load continuously at a specified loading rate until its failure.
8. Record the maximum failure load.
2. Wet (Saturated) Condition
Observation Table:
Observation Value
Diameter (D)
Length (L)
Maximum Load (P)
Calculation:
Cross Sectional Area (A) = ______
πd2
4
UCS = ______
P
A
Saturation for 7 days

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