Compaction MCQ with answer and solution

Concept

The Proctor test finds the optimum moisture content (OMC) at which soil gets its maximum dry density (MDD).

Formula

γ_d = γ / (1 + w)

Step-by-step solution

1. Compact soil samples at different water contents with fixed compactive effort. 2. Find bulk density and water content for each sample. 3. Calculate dry density using γ_d = γ / (1 + w). 4. Plot dry density against water content to get the compaction curve. 5. The peak of the curve gives the maximum dry density, and the water content at the peak is the OMC. 6. Answer is (B), maximum dry density.

Explanation

In the Proctor test, soil is compacted at different water contents. Dry density first increases and then decreases. The water content at the peak is called the optimum moisture content, and the peak value is the maximum dry density.

Why the other options are wrong

A: The test aims for maximum, not minimum, dry density. C: Specific gravity is found by the pycnometer or density bottle test. D: Porosity is not the target of the Proctor test. It is lowest near the maximum dry density.

Shortcut

Proctor test gives OMC and MDD.

Common mistake

Thinking more water always gives more density. After OMC, dry density decreases.