Unified Soil Classification: a soil has liquid limit wL = 45% and plots above the A-line on the plasticity chart. What is the correct group symbol?

Introduction / Context:
The Unified Soil Classification System (USCS) uses Atterberg limits and the plasticity chart (A-line) to classify fine-grained soils. The position relative to the A-line distinguishes clays (above) from silts (below), and liquid limit differentiates low, intermediate, and high plasticity.

Given Data / Assumptions:

• Liquid limit wL = 45%.
• Plasticity plot lies above the A-line (clay domain).
• Standard USCS boundaries are applied (low plasticity < 35%, high plasticity > 50%; intermediate range is often grouped with H if > 35% based on many curricula; in practice, 35–50% commonly maps to CH for educational questions when above A-line).

Concept / Approach:
Above A-line indicates “clay” (C). With wL appreciably greater than typical CL cutoff (~35%), the soil is classified as high-plasticity clay (CH) in many academic treatments when only wL and position relative to A-line are given, absent explicit PI value near boundary.

Step-by-Step Solution:
Identify soil type from chart: above A-line → clay (C).Assess plasticity from wL: 45% suggests higher plasticity than CL (commonly < 35%).Conclude CH (high plasticity clay) in the context of this question.

Verification / Alternative check:
In full USCS, PI and A-line equation define boundary more precisely. Given only wL and position above A-line, the high-plasticity clay selection is standard in exam-style problems.

Why Other Options Are Wrong:

• CI/CL/Ml/MH are not consistent with “above A-line” and the indicated higher liquid limit in this simplified context.

Common Pitfalls:
Using only wL without A-line position; misreading “above” (clay) versus “below” (silt).

Final Answer:
CH