Section 4: Soil and Water Conservation Engineering
Soil Mechanics
Subtopic: Soil compaction and Proctor test
Question Statement:
In the Unified Soil Classification System (USCS), a fine-grained soil with liquid limit $w_L > 50\%$ that plots ABOVE the 'A-line' ($I_P = 0.73(w_L - 20)$) on the plasticity chart is designated as:
Options:
(A) CH (Inorganic clay of high plasticity)
(B) MH (Inorganic silt of high compressibility)
(C) CL (Inorganic clay of low plasticity)
(D) OH (Organic clay of high plasticity)
Answer Key:
A
Step-by-Step Solution & Explanation
The A-line differentiates clays (above A-line) from silts and organic soils (below A-line). Liquid limit gt; 50\%$ indicates high plasticity ($H$). Thus, above A-line with $w_L > 50\%$ is classified as CH.