The document discusses various index properties of soils including specific gravity, particle size distribution, and methods for determining these properties. Specific gravity can be determined through density bottle, flask, or pycnometer methods. Particle size distribution is analyzed through sieve analysis for coarse-grained soils and sedimentation analysis for fine-grained soils. Sedimentation analysis involves allowing soil particles in suspension to settle out of water over time based on particle size.

1. CE6405 SOIL MECHANICS
V.Nageshwaran, M.E.,
Assistant Professor,
Department of Civil Engineering,
UCET

2. DETERMINATION OF INDEX PROPERTIES

3. INDEX PROPERTIES
 Water Content
 Specific Gravity
 Particle/Grain Size Distribution
 Consistency Index
 In-situ Density
 Density Index

4. SPECIFIC GRAVITY

5. SPECIFIC GRAVITY
 Specific Gravity of Soil Solids – 50 ml Density Bottle, 500 ml
Flask & Pycnometer.
 Most Accurate and Suitable for all Soil Types.
 Flask or Pycnometer – Only for Coarse Grained Soils.
 Density Bottle Method – Standard Method – Laboratory.
 Sequence of Observation – Same in all the 3 Methods.

6. CONT…
 Mass of Empty – Dry – Bottle/Flask/Pycnometer, M1.
 Oven Dried Soil Sample – Cooled in Desiccator +
Bottle/Flask/Pycnometer, M2.
 Fill the Bottle with Distilled Water/Kerosene – gradually – Remove
Entrapped Air either by applying Vacuum or by Shaking the
Bottle.
 Mass of Bottle + Soil + Water (Full upto the Top), M3.
 Empty completely and thoroughly washed.
 Fill the Bottle with Clean Water/Kerosene full upto top and weigh,
M4.

7. CONT…
12d MMM 
23w3 MMM 
14w4 MMM 
   2314sw MMMMM 
   2314
12
s
MMMM
MM
VolumeEqualofWaterofMass
SoilofMassDry
G



     43d
d
4312
12
s
MMM
M
MMMM
MM
G





 Assignment – Fine Grained Soil.
    C27atWaterofSp.Gr.
CTatWaterofSp.Gr.
.CTatGC27atG ss 




8. PARTICLE SIZE DISTRIBUTION

9. PARTICLE SIZE DISTRIBUTION
 Particle Size or Mechanical Analysis.
 Dry Soil Sample – Separated into various Particle size
fractions and each of the fraction is expressed as %.
 Mechanical Analysis
1) Sieve Analysis – Coarse Grained Soils only.
2) Sedimentation or Wet Mechanical Analysis – Fine Grained
Soils only.
 Both Analysis – Necessary.
 Sieve Analysis – True Representative of GSD – No influence
of Temperature.

10. SIEVE ANALYSIS
 In BS & ASTM Standards – Sieve Sizes – No. of Openings
per inch.
 In IS: 460-1962 – Sieve Sizes – Designated by Size of the
Aperture in mm.
 Complete Sieve Analysis – Coarse Analysis & Fine
Analysis.
 Coarse Analysis – Gravel > 4.75 mm.
 Sieve Set – IS: 100, 63, 20, 10 and 4.75 mm.
 Fine Analysis – Sand, Silt & Clay < 4.75 mm.
 Sieve Set – IS: 2 mm, 1 mm, 600 µ, 425 µ, 300 µ, 212 µ,
150 µ and 75 µ.
Sieve
Analysis
Coarse
Analysis
Fine
Analysis

11. CONT…
 Performed by arranging various Sieves one over the other –
Order of Mesh Openings – Largest Aperture at Top &
Smallest at Bottom – Pan/Receiver kept at Bottom &
Lid/Cover kept at Top.
 Assemble the Sieves as said above.
 Soil Sample – Put on Top Sieve – Fit the Assembly on a
Sieve Shaking Machine.
 Amount of Shaking depends on the Shape and No. of
Particles.
 At least 10 mins of Shaking is Desirable – Soils with small
Particles.
 Portion of Soil Sample retained on each Sieve is Weighed.
 % of Soil retained on each Sieve – Calculated – Basis of
Total Mass of Soil Sample taken.
 Results - % Passing through each Sieve – Calculated.

12. CONT…
 Advisable – Wash the Soil Portion passing through 4.75 mm
Sieve over 75 µ Sieve – Silt and Clay particles sticking to
Sand particles may be dislodged.
 Washing – Continue until – Water passing through 75 µ
Sieve – Substantially Clean.
 2 g of Sodium Hexametaphosphate (SHMP) – added to per
litre of water used.
 Fraction retained on 75 µ Sieve – Dried in Oven.
 Dried Portion – Re-Seived through 2 mm, 1 mm, 600 µ, 425
µ, 300 µ, 212 µ, 150 µ & 75 µ IS Sieves.
 Portion passing through 75 µ Sieve (While Washing) – Dried
Separately – Mass determined - % Finer than 75 µ Size.
 Portion passing 75 µ Size – Substantial (50%) – Wet
Analysis is done – Further Sub-division of Particle Size
Distribution (PSD).

13. SAMPLING OF SOIL

14. SIEVE SET CONFIGURATION
Sl.
No.
Sieve size
1 Lid
2 2 mm
3 1 mm
4 600μm
5 425μm
6 300μm
7 212μm
8 150μm
9 75 μm
10 Pan
1 mm
2 mm
600 μm
2 mm
75 μm
Lid
Receiver
or Pan

15. MANUAL SIEVING

16. Sieve Shaker

18. PARTICLE SIZE DISTRIBUTION
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1 10 100
Particle Size
Weight%ofParticles<d
Sieving
Hydrometer
Log-Scale
10
60
u
D
D
C   
6010
2
30
c
DD
D
C

&

19. PARTICLE SIZE DISTRIBUTION CURVE

20. SEDIMENTATION ANALYSIS –
 Wet Mechanical/Sedimentation Analysis – Carried out – Soil
Fraction, Finer than 75 µ Size kept in Suspension in a Liquid
Medium – Usually Water.
 Analysis is based on Stoke’s Law – Velocity at which
Grains/Particles settle out of Suspension, (all other factors
remains unchanged) depends on the Shape, Weight & Size
of the Grain/Particle.
 Soil Particles – Assumed to be Spherical & Same Specific
Gravity (avg.) – Hence Coarser particles settle more quickly
than Finer ones.
 v – Terminal Velocity of Sinking of a Spherical Particle.
η
γγ
r
9
2
v ws2 
 or
η
γγ
D
18
1
v ws2 
 m/s
g
μ
η  2
s/m-kN μ poisein
THEORY

21. CONT…
 If Water is used –
 Similarly,
 Express only in m, s & kN.
 If Diameter, D of the Particle – mm.
 
η
γ1G
D
18
1
v ws2 
 m/s
3
w kN/m9.81γ 
wss γGγ 
η
γγ
D
18
1
v ws2 
 m/s
 
η
γ1G
1000
D
18
1
v ws
2








 
η1018
γ1GD
v 6
ws
2



 
η101.835
1GD
v 6
s
2


or
 
mm
γ1G
η.v1018
D
ws
6



 
mm
1G
η.v
1355D
s 
or

22. CONT…
 1 poise
 If a particle of diameter D mm falls through a height He cm in
t mins.
2
s/m-N1.0
m/s
6000t
H
cm/s
60t
H
v ee

 
mm
.t.γ1G
η.H3000
D
ws
e


24
s/m-kN01 

 
mm
γ1G
η.v1018
D
ws
6



 
mm
6000t
H
γ1G
η1018
D e
ws
6




mm
t
H
F10D e5

 
mm
.γ1G
η3000
10F
ws
5

 KnownG&n s
Factor
Constant

23. CONT…
 F – Constant Factor – Depends on – depends on
Temperature.
 F also depends of Temperature – Given for various Gs &
Temp.
sG&η

24. CONT…
 At 27˚C, µ of Distilled Water ≈ 0.00855 poise.
2-4
s/m-kN100.00855η 
68.2Gs 
 
η1018
γ1GD
v 6
ws
2


&
 
46
2
100.008551018
9.8112.68D
v 



m/s1.077Dv 2


25. CONT…
 Both – Suitable amount of Oven dried Soil Sample < 75 µ Size
– Mixed with given Volume of Distilled Water.
 Mixture – Shaken thoroughly – Jar containing Soil Water
Mixture – Kept Vertical throughout the Test.
 Soil Particles – Assumed to be Uniformly Distributed throughout
the Suspension.
 After Time Interval t – Sample the Soil Suspension at a Height
He (Measured from Top Level of Suspension).
 Particle in Suspension < Size of Particle that Settled Down.
 Diameter of Particle Finer than the Settled ones can be
determined.
Sedimentation
Analysis
HydrometerA
nalysis
Pipette
Analysis
mm
t
H
F10D e5


26. CONT…
 > t allowed for Suspension to Settle – Finer the Particle Sizes
retained at this Depth, He.
 Sampling at different time intervals at this Sampling Depth, He –
gives the Content of Particles of different Sizes.
 where, N = % Finer than the Diameter, D; MD = Mass per ml of
all particles small than the Diameter, D; Md = Total Dry Mass of
all particles put in the Suspension; V = Volume of Suspension.
mm
t
H
F10D e5

100
V
M
M
N
d
D

100
V
M
M
N
d
D
&

27. LIMITATIONS OF SEDIMENTATION ANALYSIS
 Assumptions
1. Soil Particles are Spherical.
2. Particles Settle Independent of other particles and Neighbour particles
do not have any effect on its Velocity of Settlement.
3. Walls of Jar, in which the Suspension is kept also do not affect the
Settlement.
 Actual Practice – Fine Particles of Soil – Not Truly Spherical – Thin
Platelets – Do not Settle out of Suspension in the Same Manner and at
the Same Rate as Smooth Spheres – Sedimentation Analysis gives the
Particle Size Equivalent Diameter.
 Validity of Law < 0.2 mm Eq. Dia. (Upper Limit of Particle Size).
 Particle Size > 0.2 mm – Liquid tends to develop Turbulent Motion at
the Boundaries of Particles.
 Validity of Law > 0.0002 mm Eq. Dia. (Lower Limit of Particle Size).
 Particle Size < 0.0002 mm – Brownian Movement affects Settlement –
Stoke’s Law Fails.

28. CONT…
 Assumption – Average Specific Gravity – May Vary – different Mineral
Constituents.
 Settlement of the Particles – influenced by the Surrounding Particles –
Liquid is not of Infinite Extent.
 Particles falling near the Wall of Jar – Affected.

33. PRINCIPLE OF SEDIMENTATION ANALYSIS
All particles are
in suspension
Only Silt and Clay
particles are
in suspension
Only Clay
particles are
in suspension

34. PIPETTE ANALYSIS
 Standard Sedimentation Method used in the Laboratory.
 Consists of Pipette, Jar, No. Sampling Bottles.
 Boiling Tube of 500 ml Capacity may be used in the place of
Jar.
 Pipette consists of
 125 ml Bulb with Stop Cock, for keeping Distilled Water.
 3 Way Stop Cock
 Suction and Waste Water Outlets
 Sampling Pipette of 10 ml Capacity (inclusive of Cock’s
capacity).
 Method – Draw off Samples of Soil Suspension, 10 ml in
Volume, by means of this Pipette from a depth of 10 cm (He)
at various Time Intervals after the Commencement of
Sedimentation.
 Recommended Time Intervals – ½, 1, 2, 4, 8, 15 and 30
mins & 1, 2, 4, 8, 16 and 24 h.

35. CONT…
 Pipette – Inserted into the Boiling Tube – about 25 s
before the selected time interval.
 Time taken for Sampling (Sucking the Sample) < 10 to
20 s.
 Each Sample taken – Transferred to Suitable Sampling
Bottles and Dried in an Oven.
 Mass MD of Solids per ml of Suspension – Found by
taking the Dry Mass and Dividing it by 10.

36. CONT…
Method of Preparing Soil Suspension
 < 75 µ Size – Included – Soil Sample is Washed through a 75 µ
Sieve.
 General – 12 to 30 g of Oven-Dried Soil Sample – Weighed
Accurately and Mixed with Distilled Water in a Dish or Beaker
to form a Smooth Thin Paste.
 Sample Size – Depend on Type of Soil.
 Proper Dispersion of Soil – Dispersing Agent (Deflocculating
Agent) – Added to Soil.
 Dispersing Agent – Sodium Oxalate, Sodium Silicate, Sodium
Polyphosphate Compounds [Sodium Pyrophosphate, Sodium
Hexametaphosphate (Calgon) & Sodium Tripolyphosphate].
 IS:2720 (Part IV)-1965 – recommends – Dispersing Solution
containing 33 g of SHMP and 7 g of Sodium Carbonate in
Distilled Water to make 1 l of Solution.

37. CONT…
 25 ml of Solution – Added to Dish (Soil + Distilled Water) –
Mixture – Warmed gently – 10 mins.
 Transfer the Contents to the Cup of a Mechanical Mixer – Use
Jet of Distilled Water to Wash all Traces of the Soil out of the
Evaporating Dish.
 Stir well the Soil Suspension ≥ 15 mins (If Highly Clayey Soils).
 Wash the Suspension through a 75 µ Sieve – Use Jet of
Distilled Water.
 Suspension which has passed through the 75 µ Sieve –
Transferred to 500 ml Capacity Boiling Tube. Precise Care
required.
 Fill the Boiling Tube upto 500 ml mark – adding Distilled Water.
 Put the Tube in a Constant Temperature Water Bath.
 When Temperature of Boiling Tube = Water Bath – Shake and
Invert the Tube several times and replace in the Bath.

38. CONT…
 Start the Stop Watch.
 Collect the Soil Samples at various Time Intervals – Help of
Pipette.
 Soils – Containing Organic Matter and Calcium Compounds –
Pretreat before the addition of the Dispersing Agent – May act
as Cementing Agent – Cause the particles to settle as
Aggregations of Particles instead of Individuals.
 Pretreatment – Process of Removal of Organic Matter and
Calcium Compounds.
 1st – Treat the Soil – H2O2 – Remove Organic Matter – Oxidation.
 Mixture – Soil + H2O2 – Kept Warm at a Temp. ≤ 60˚C – Till no
further Evolution of Gas.
 Decompose – Remaining H2O2 – by Boiling the Solution.
 2nd – Treat the Cooled Soil – 0.2 N HCl Acid – Remove Calcium.

39. CONT…
 After the Completion of the Reaction – Filter the Mixture – Wash
the Filtrate with Distilled Water – Till Free of Acid.
 Dry the Filtrate in Oven – Calculate the Loss of Mass due to
Pretreatment.
 Calculation of D & N
 10 ml Sample – Collected from a Depth of 10 cm – With Pipette
– various time intervals.
 Collected Sample – taken in Weighing Bottles (Sampling Bottles)
– Dry in Oven.
 where, Vp = Vol. of the Pipette = Vol of Sample Collected = 10
ml.
p
D
V
BottleWeighingin theSampleofMassDry
M 
100
V
M
V
m
M
N
d
D




40. CONT…
 where, m = Mass of Dispersing Agent present in the Total
Volume of Suspension, V; V = Vol. of Suspension = 500 ml; N =
% Finer, based on Md.
 Example:
 If 25 ml of Dispersing Agent – 33 g SHMP +7 g of Sodium
Carbonate per l.
1g25
1000
733
m 



41. LIMITATIONS OF PIPETTE ANALYSIS
 Very Simple – More Time – Not Suitable for Routine Control
Tests.
 Apparatus – Very Sensitive &Very Accurate Weighing
required – Difficult.

43. HYDROMETER ANALYSIS
 Fine Grain Analysis – Principle same as that of Pipette
Method.
 Method of Observation differs.
 Weight of Solids, MD – Present at any time – Calculated
indirectly by reading the density of Soil Suspension.
 Calibrate Hydrometer – Relationship between Hydrometer
reading Rh on the Stem and the Effective Depth, He for a
given Hydrometer.
 Effective Depth – Distance from the Surface of Soil
Suspension to the Level at which the Density of Soil
Suspension is being Measured.
 He increases particles settle with time.
 Reading of Graduated Stem of Hydrometer – Density of Soil
Suspension at the Centre of the Bulb BB at any instant of
time.

45. HYDROMETER ANALYSIS

46. CONT…
 As Specific Gravity of the Soil Suspension is close to Unity –
Usual Practice to Subtract 1 from the Specific Gravity and Multiply
the Balance by 1000.
 Example: Density Reading of 1.025 is on the Hydrometer Stem –
Record it as 25 (i.e. Rh = 25).
 Both Hydrometer reading and Density Reading increase in the
downward direction towards the Hydrometer Bulb.
 Let h be Height of Bulb; H be the Distance in cm (between any
Hydrometer reading Rh and neck); Vh be Volume of Hydrometer
Bulb.
 As the Hydrometer is immerse in the jar – Water level rises.
 If A is C.S. Area of Jar – Surface of Soil Suspension rises by Vh/A,
whereas the Centre of the Hydrometer Bulb (b1b1), water rises
approximately by Vh/2A.
 But Soil Particle at b1b1 is same as that of bb.













A
V
h
2
1
H
A
V
2A
V
2
h
HH hhh
e

47. CONT…
 Volume of Hydrometer, Vh in ml = Mass of Hydrometer in g.
 h, Vh and A – Constant.
 H to be measured using a Graduated Scale.

49. CONT…
 Test Procedure – Preparation of Soil Suspension is same
as that of Pipette Method.
 Volume of Suspension – 1000 ml.
 So, Double the Quantity of Dry Soil and Dispersing Agent.
 Sedimentation Jar – Cylinder – shaken vigorously – kept
vertical over a solid base.
 Stop Watch – Simultaneously Started.
 Insert Hydrometer slowly in the Jar.
 Take readings at 0.5, 1 and 2 mins intervals.
 Take out the Hydrometer.
 Further readings are taken at the interval of 4, 8, 15, 30 mins
and 1, 2, 4 h etc by inserting the Hydrometer about 30 sec
before the given interval – So that it is stable at the time
when the reading is to be taken.

50. CONT…
 Soil Suspension – Opaque – Reading taken Corresponding to the
Upper Level of the Meniscus.
 Suitable Meniscus Correction is then applied to the Hydrometer
Readings.
 Correction to the Hydrometer Readings – Temperature
Correction, Meniscus Correction and Dispersing Agent
Correction.
 Temperature Correction
 Generally, Calibrated at a Temperature of 27˚C.
 If the Temperature of the Soil Suspension ≠ 27˚C – Temperature
Correction, Ct – required.
 If the Test Temperature > 27˚C – Hydrometer Reading is Less –
Positive Correction – required.
 If the Test Temperature < 27˚C – Hydrometer Reading is More –
Negative Correction – required.

51. CONT…
 Meniscus Correction – Soil Suspension – Opaque –
Hydrometer Reading is taken at the top of Meniscus.
 Actual Reading – to be taken at Water Level – Which will be
more – Since readings increase in Downward direction.
 Meniscus Correction, Cm – Positive (always).
 Magnitude found by Immersing Hydrometer in a Jar
containing Clear Water – Find the difference between the
Reading corresponding to the Top & Bottom of the Meniscus.
 Dispersing Agent Correction – Addition of Dispersing
Agent in Water increase its density – Cd is Negative
(always).
 Corrected Hydrometer Reading, R = Rh’+ Cm ± Ct – Cd
 Rh’ = Observed Hydrometer Reading at the Top of the
Meniscus.

52. CONT…
 All 3 Corrections – Combined into One Correction –
Composite Correction, ± C.
 R = Rh’ ± C
 R = Rh’ ± Cm – Required for determining the Effective Depth
from the Calibration Chart.
 To find the Composite Correction, C – Identical Cylinder with
100 ml capacity is taken – filled with distilled water & same
quantity of dispersing agent is used in the test cylinder.
 Temperature of Both Cylinder – Should be same.
 Immerse Hydrometer in the Comparison Cylinder – Distilled
water + Dispersing Agent – Take reading at the top of the
Meniscus.
 Negative of the Hydrometer Reading so obtained gives the
Composite Correction, C.

53. CONT…
 Computation of D and N
 Particle Size
 For various time intervals Rh is found and corresponding He
can found from the Chart.
 Substitute He cm and t mins – D mm can be obtained.
 To Find the % of Soil Finer than D
mm
t
H
F10D e5

 Total Mass of Suspension
in 1 ml, M = MW + MD
 MW = 1 – (MD/Gs)
 So, M = 1 – (MD/Gs) + MD
 Mass of Solids in 1ml
Suspension, MD at
Effective Depth, He is
 Hydrometer reading, R =
(ρ – 1) × 1000
1000
R
1ρ 

54. CONT…
 Mass of Solids in 1ml Suspension, MD at Effective Depth, He
is
 Since Volume is same: Mass of Suspension and Density is
also same.
D
s
D
M
G
M
1
1000
R
1ρ 






D
s
D
M
G
M
1
1000
R
1 














1G
G
1000
R
M
s
s
D
100
V
M
M
N
d
D

Take Volume, V = 1000 ml
R
1)(GM
100G
N
sd
s'




55. CONT…
 For Combined Sieve and Sedimentation Analysis.
 If M is the Total Dry Mass of Soil originally taken (Before
Sieving it over 2 mm Sieve) – Overall % Finer N is
 M’ – Cumulative Mass passing 2 mm Sieve (Out of which the
Soil having Mass, Md was taken for the Wet Analysis)
 M – Total Dry Mass of Soil Sample.
 If the Soil Sample does not contain Particles Coarser than 2
mm size then N = N’.
M
M
NN
'
'


57. PARTICLE SIZE DISTRIBUTION CURVE
 Result of Mechanical Analysis – Sieve and Sedimentation
Analysis – PSD Curve – % Finer, N as Ordinate & Particle
Diameter (Log Scale) as the Abscissa.
 Type & Gradation of Soil.
 Left – Fine.
 Right – Coarse.
 Well Graded.
 Poorly Graded.
 Uniformly Graded.
 Gap Graded or Skip Graded.
 Coarse Grained Soil – D10, D30 & D60.
 Effective Size or Diameter, D10 – mm 10 % of the Particles <
than this Size.
 D30 – mm 30 % of the Particles < than this Size.
 D60 – mm 60 % of the Particles < than this Size.
10
60
u
D
D
C 
 
6010
2
30
c
DD
D
C

&

58. PARTICLE SIZE DISTRIBUTION
0
10
20
30
40
50
60
70
80
90
100
0.001 0.01 0.1 1 10 100
Particle Size
Weight%ofParticles<d
Sieving
Hydrometer
Log-Scale
10
60
u
D
D
C   
6010
2
30
c
DD
D
C

&

59. PARTICLE SIZE DISTRIBUTION CURVE