1. Geotechnical Engineering: Practical Size Analysis
Mr. Rohan Dashupta, Asst. Professor
Department: B.E. Civil Engineering
Subject: Geotechnical Engineering - I
Semester: V
Teaching Aids Service by KRRC Information Section

2. Particle Size or grain size refers to the diameter of a grain of soil.
INTRODUCTION
Particle Size or grain size refers to the diameter of a grain of soil.

3. INTRODUCTION
Particle Size Analysis or Mechanical Analysis is the determination percentage of various sizes of particles in a given dry soil sample.
It is the separation of soil into different size fractions.

4. Sedimentation Analysis or Wet Mechanical Analysis
TYPES OF PARTICLE SIZE ANALYSIS
There are 2 types of Particle Size Analysis:
Sieve Analysis
Sedimentation Analysis or Wet Mechanical Analysis

5. Sieves used for Sieve Analysis
Mechanical Sieve Shaker

6. SIEVE ANALYSIS Course Analysis
The portion of soil retained on 4.75 mm sieve is termed as gravel fraction and is kept for the course analysis.
Fine Analysis
The portion of soil passing through 4.75 mm sieve is termed subjected to fine analysis.
4.75 mm sieve

7. SIEVE ANALYSIS: INDIAN STANDARDS
Indian Standard Specification for Test Sieves
Course Sieve Analysis
Fine Sieve Analysis
100 mm
2 mm
63 mm
1 mm
20 mm
600 micron
10 mm
425 micron
4.75 mm
300 micron -
212 micron
150 micron
75 microns

8. SIEVE ANALYSIS: OBSERVATION TABLE
Sr.
No. IS
Sieve
Particle Size
D (mm)
Mass
Retained (gm) %
Retained
Cumulative
% Retained
% Finer (N)

9. SIEVE ANALYSIS: CALCULATION
% Retained =
(Mass Retained / Total Mass of Dry Soil Sample) x 100
Cumulative % Retained =
Current % Retained + Previous % Retained
Cumulative % Finer =
100 – Cumulative % Retained

10. Total Mass of Dry Soil Sample = 1000 gm
Example
Total Mass of Dry Soil Sample = 1000 gm
Mass of Soil passing through 75 micron = 77 gm
Sr.
No. IS
Sieve
Particle Size
D (mm)
Mass
Retained (gm) %
Retained
Cumulative
% Retained
% Finer (N) 1.
100 mm -
100 2.
63 mm 3.
20 mm 33
3.3
96.7 4.
10 mm 49
4.9
8.2
91.8 5.
4.75 mm 85
8.5
16.7
83.3 6.
2 mm
140 14
30.7
69.3 7.
1 mm
160 16
46.7
53.3 8.
600 μm
0.6 mm
142
14.2
60.9
39.1 9.
425 μm
0.425 mm
118
11.8
72.7
27.3
10.
300 μm
0.3 mm 82
80.9
19.1
11.
212 μm
0.212 mm 56
5.6
86.5
13.5
12.
150 μm
0.15 mm 35
3.5 90
10.0
13.
75 μm
0.075 mm 23
2.3
92.3
7.7

11. PARTICLE SIZE DISTRIBUTION CURVE
The results of the mechanical analysis are plotted to get a particle size distribution curve with the percentage finer N on the Y-axis and particle diameter on the X-axis, the diameter being plotted on a logarithmic scale.
The particle size diameter curve gives us an idea about the type and gradation of the soil.
A curve situated higher up or to the left represents a relatively fine grained soil.
A curve situated to the right represents a course grained soil.
continued...

13. PARTICLE SIZE DISTRIBUTION CURVE
Well Graded Soil = good representation of particles of all sizes
Poorly Graded Soil = excess of certain particles and deficiency of other.
Uniformly Graded Soil = most of the particles of the same size
Gap Graded or Skip Graded Soil = intermediate particle sizes are missing

14. PARTICLE SIZE DISTRIBUTION CURVE
For coarse grained soil, certain particle sizes such as D10, D30 and D60 are important.
D10 represents a size, in mm such that 10% of the particles are finer than this size. The size D10 is sometimes called the effective size or effective diameter.
D30 represents a size, in mm such that 30% of the particles are finer than this size.
D60 represents a size, in mm such that 60% of the particles are finer than this size.