3 Classify the following three soils based on the following

3. Classify the following three soils based on the following particle size analysis results and Atterberg limits test results in accordance with the USCS and USDA 100 80 Sample1 Sample2 Sample3 60 C 40 20 0 10 0.01 1E-3 Particle diameter (mm) PL 31 10 NA 01 61 37 NA

Solution

USCS classification system

Soil 1.

% Passing no.200 (0,075mm) sieve = 100%, so it is fine grained soil

LL = 61 >50, and PI = 61-31= 30,

On A-line, PI = 0.73(61-20) = 29.93, So it plots above A-line, so it is CH (Fat Clay)

Soil 2

Soil passing 0.075mm = 51%, so it is fine grained soil,

LL = 37 <50, PI = 37-10 = 27,

On a-line, PI = 0.73(37-20) = 12.41, so it plots above A-line.

So the soil is CL(Lean slay)

Soil 3

Soil passing 0.075mm = 0%,

% passing no.4 sieve = 97%, so it is sand,

D10 = 0.35mm, D30 = 0.60mm and D60=0.9,

so Cu = D60/D10 = 0.9/0.35 = 2.571 <6, so not a well graded soil.

So the soil is SP (Poorly graded sand)

Please note that the second classification USDA does not work on the particle size, but it is governed by the soil properties and soil mineral compositions.