Class notes of Geotechnical Engineering course I used to teach at UET Lahore. Feel free to download the slide show. Anyone looking to modify these files and use them for their own teaching purposes can contact me directly to get hold of editable version.

1. 1
Geotechnical Engineering–I [CE-221]
BSc Civil Engineering – 4th Semester
by
Dr. Muhammad Irfan
Assistant Professor
Civil Engg. Dept. – UET Lahore
Email: mirfan1@msn.com
Lecture Handouts: https://groups.google.com/forum/#!forum/geotech-i
Lecture # 7
14-Feb-2017

2. 2
US STANDARD SIEVE SIZES
Sieve No. Opening (mm) Sieve No. Opening (mm)
3 inch 76.200 20 0.850
2 inch 50.800 25 0.710
1.5 inch 38.100 30 0.600
1 inch 25.400 35 0.500
3/4 inch 19.000 40 0.425
3/8 inch 9.520 50 0.355
4 4.750 60 0.250
5 4.000 70 0.212
6 3.350 80 0.180
7 2.800 100 0.150
8 2.360 120 0.125
10 2.000 140 0.106
12 1.700 170 0.090
14 1.400 200 0.075
16 1.180 270 0.053
18 1.000

3. 3
SIEVE ANALYSIS – Procedure
• Soil used in sieve analysis is oven-dried and all lumps are
broken.
• A stack of sieves (sieve nest), with sieve opening of
decreasing size from top to bottom, is arranged.
• A pan is placed below the stack.
• The soil is then shaken through this sieve nest.
• Mass retained on each sieve is determined.
Wet Sieving Technique
Breaking lumps in clayey soils may be difficult. If soils contain silts and
clays, the wet sieving is usually used to preserve the fine content.
In this case, the soil may be mixed with water to make a slurry and then
washed through sieves.
Portions retained on each sieve are collected separately and oven-dried.

4. 4
76.2 mm
4.75 mm
0.075 mm
Pan
100 %
Finer (Passing)
93 %
62 %
0 %
Gravel
Sand
Silt and Clay
100 – 93 = 7%
93 – 62 = 31%
62 – 0 = 62%
Gravel
Sand
Silt and Clay
SIEVE ANALYSIS – Procedure

5. 5
CumulativePercentagepassing
througheachsieve(%)
Grain Diameter (mm)
Log scale
SIEVE ANALYSIS – Results
(Gradation Curve)

6. 6
SIEVE ANALYSIS – Calculations
Sieve
No.
Diameter
(mm)
Wt. of soil
retained
(gm)
Cumulative
soil weight
retained on
each sieve
(gm)
Cumulative
percentage
retained (%)
Cumulative
percentage
passing (%)
(Col. 1) (Col. 2) (Col. 3) (Col. 4) (Col. 5) (Col. 6)
(Col. 4) = (Col. 3) + (Col. 4) of previous line
(Col. 5) = [(Col. 4)/Total wt.] x 100
(Col. 6) = 100 – (Col. 5)

7. 7
SIEVE ANALYSIS – Example

8. 8
SIEVE ANALYSIS – Example

9. 9
0
10
20
30
40
50
60
70
80
90
100
0.010.1110
PercentFiner%
Particle Size (mm)
SIEVE ANALYSIS – Example

10. 10
SOIL GRADATIONS
• Well graded soils
• Poorly graded soils
• Uniformly graded soils
• Gap graded soils

11. 11
GRAIN SIZE DISTRIBUTION CURVE
Well-graded soil
Poorly-graded
(uniformly graded) soil

12. 12
D10, D30, and D60
10
Percentpassing
30
60
Grain Diameter
D60 D30 D10
D10= Diameter corresponding to 10% passing
D30= Diameter corresponding to 30% passing
D60= Diameter corresponding to 60% passing
D50= Diameter corresponding to 50% passing
= Mean diameter of soil sample

13. 13
COEFFICIENTS OF GRADATION
Coefficient of Uniformity
Coefficient of Curvature
10
60
D
D
Cu 
 1060
2
30
DD
D
Cc


)(6
)(4
31
sandsforC
gravelsforC
and
C
u
u
c



For a well-graded soils

14. 14
What is the Cu for a soil with only one
grain size?
POINT TO PONDER!!!

15. 15
D
%Finer
1
D
D
C
uniformityoftCoefficien
10
60
u 
Grain Size Distribution
Cu of Uniformly Graded Soil

16. 16
GRAIN SIZE DISTRIBUTION CURVE
100 10 1 0.1 0.01 0.001
A
D
C
E
B
#200#43”
A: fine-grained soils
B: coarse-grained soils
Cu = 5
Cc = 0.8
Cu = 13
Cc = 0.83

17. 17
100 10 1 0.1 0.01 0.001
A
D
C
E
B
#200#43”
C: poorly graded or
uniformly graded
Cu = 1.63
Cc = 0.96
GRAIN SIZE DISTRIBUTION CURVE

18. 18
100 10 1 0.1 0.01 0.001
A
D
C
E
B
#200#43”
D: well-graded soils
E: gap-graded soils
Cu = 190
Cc = 1.18
Cu = 111
Cc = 0.18
GRAIN SIZE DISTRIBUTION CURVE

19. 19
SIEVE ANALYSIS – Calculations
Sieve
No.
Diameter
(mm)
Wt. of soil
retained
(gm)
Cumulative
soil weight
retained on
each sieve
(gm)
Cumulative
percentage
retained (%)
Cumulative
percentage
passing (%)
(Col. 1) (Col. 2) (Col. 3) (Col. 4) (Col. 5) (Col. 6)
(Col. 4) = (Col. 3) + (Col. 4) of previous line
(Col. 5) = [(Col. 4)/Total wt.] x 100
(Col. 6) = 100 – (Col. 5)

20. 20
SIEVE ANALYSIS
(Practice Problem)

21. 21
SIEVE ANALYSIS
(Practice Problem)

22. 22
SIEVE ANALYSIS
(Practice Problem)
0
10
20
30
40
50
60
70
80
90
100
0.010.1110
%Finer
Grain size (mm)
D10=0.09 mm
D30=0.27 mm
D60=0.58 mm
Cu = 6.44
Cc = 1.40

23. 23
SIEVE ANALYSIS
(Practice Problem)
0
10
20
30
40
50
60
70
80
90
100
0.010.1110
%Finer
Grain size (mm)
98%
49%
Medium sand → (2.0 mm – 0.425 mm)
%age of medium sand = 98-49 = 49%
%age of gravel (75 - 4.75 mm)
%age of coarse sand (4.75 - 2.0 mm)
%age of medium sand (2.0 – 0.425 mm)
%age of fine sand (0.425 – 0.075 mm)
%age of silt and clay (passing sieve #200)
= nil
= 2
= 49
= 43
= 6

24. 24
0
20
40
60
80
100
0.0010.010.1110
Percentpassing
Grain diameter (mm)
Grain-size distribution curve
GRAVEL SAND
SILT or CLAY
Coarse Fine Coarse Medium Fine
3/4 in. No.4 No.10 No.40 No.200 Hydrometer3 in.
D10 = 0.10 mm
D30 = 0.18 mm
D60 = 0.25 mm
Cu = 2.50
Cc = 1.30

25. 25
Coarse-grained soils:
Gravel Sand
Fine-grained soils:
Silt Clay
0.075 mm (USCS)
0.06 mm (BS)
Sieve Analysis Hydrometer Analysis
MECHANICAL ANALYSIS OF SOIL
Mechanical analysis is the determination of the size range of particles present
in a soil, expressed as a percentage of the total dry weight.

26. 26
HYDROMETER ANALYSIS –
Stoke’s Law
For a sphere moving in a fluid, the drag force acting on it is a
function of its diameter.
Stoke’s Law
V1 V2<
→ Silt will settle faster compared to
clay.
→ Why soil particles settle in water?

27. 27
HYDROMETER ANALYSIS –
Conceptual Basis
→ Soil settles down
→ Gs of the solution decreases
→ Hydrometer settles in water

28. 28
• At any time t, hydrometer measures the
specific gravity of the suspension near the
vicinity of its bulb (depth L).
• For pure water hydrometer reading will be 1.
• It indirectly gives the amount of soil that is
still in suspension.
• By knowing the amount of soil in
suspension, L, and t, we can calculate the
%age of soil by weight finer than a given
diameter.
HYDROMETER ANALYSIS

29. 29
R
L
HYDROMETER ANALYSIS
(cm)164.029.16(cm) RL 
where, R = hydrometer reading corrected for meniscus
For ASTM 152H hydrometer
How to correlate L with particle size?
Corrected hydrometer reading;
Rc = Ractual – Zero Correction + Temp. Correction
100


s
c
W
aR
finerPercent
a = correction factor for specific gravity
Ws = Total weight of soil specimen
Zero correction = correction due to the use of deflocculating agent

30. 30
CONCLUDED
REFERENCE MATERIAL
Principles of Geotechnical Engineering (7th Edition)
By Braja M. Das
Chapter #2