The field identification test results for a soil are given below. What is the Unified Soil Classification System (USCS) for this soil? More than 90% by wieght larger than No. 200 sieve More than half of the course fraction is smaller than 1/4 inch There is a wide range of grain sizes, with all intermediate sizes present Solution If more than 50% of soil is retained on the Seive No.200, the soil is designated as coarse grained, otherwise fine grained. In this case 90% soil is retained on No 200 seive. Hence the soil is coarse grained Coarse grained soils can be further calssified in to gravel and sand according to the particle size. If 50% or more of coarse fraction is retained on No.4 (4.75mm) seive,soil is designated as gravel. If more than 50% pass through the seive No.4, the soil is sand. In this case more than 50% coarse fraction pass through 1/4 inch (6.35 mm). As no other datas are given, we may have to assume that more than 50% coarse fraction pass through 4.75 mm also. Hence the soil can be classified as sand. The soil is containing wide range of grain size, with all intermediate sizes. Hence the soil is well graded. (No details about the % of fines is given in the question) The soil according to USCS classification an be designated as WELL GRADED SAND (SW)..

1. The field identification test results for a soil are given below. What is the Unified Soil
Classification System (USCS) for this soil?
More than 90% by wieght larger than No. 200 sieve
More than half of the course fraction is smaller than 1/4 inch
There is a wide range of grain sizes, with all intermediate sizes present
Solution
If more than 50% of soil is retained on the Seive No.200, the soil is designated as coarse grained,
otherwise fine grained. In this case 90% soil is retained on No 200 seive. Hence the soil is coarse
grained
Coarse grained soils can be further calssified in to gravel and sand according to the particle size.
If 50% or more of coarse fraction is retained on No.4 (4.75mm) seive,soil is designated as gravel.
If more than 50% pass through the seive No.4, the soil is sand. In this case more than 50% coarse
fraction pass through 1/4 inch (6.35 mm). As no other datas are given, we may have to assume
that more than 50% coarse fraction pass through 4.75 mm also. Hence the soil can be classified
as sand.
The soil is containing wide range of grain size, with all intermediate sizes. Hence the soil is well
graded. (No details about the % of fines is given in the question)
The soil according to USCS classification an be designated as WELL GRADED SAND (SW).