The sieve analysis of a soil gave the following results: % passing 75μ sieve = 4, % retained on 4.75 mm sieve = 50, Coefficient of curvature = 2, Uniformity coefficient = 5 Classify the soil as per ISC system.
- AGWCorrect
- BGM
- CGP
- DSC
Solution
Concept
Classification of coarse soils
Step-by-step solution
1. Fines 4% (< 5%), so the soil is clean. 2. Retained on 4.75 mm = 50% of the whole sample, i.e. 52% of the coarse fraction: gravel. 3. Cu = 5 (≥ 4) and Cc = 2 (1–3): well graded. 4. Hence GW.
Explanation
Clean, gravelly, well graded.
Why the other options are wrong
GM has fines; GP is poorly graded; SC is sand with clay fines.
Shortcut
<5% fines, Cu ≥ 4, 1 ≤ Cc ≤ 3 → GW.
Correct answer: A) GW