Bearing Capacity of Soil MCQ with answer and solution

Concept

Local shear failure happens in loose or soft soils that are highly compressible.

Formula

For local shear (Terzaghi): c_m = (2/3)c, tan φ_m = (2/3) tan φ

Step-by-step solution

1. Terzaghi gives three failure modes: general shear, local shear and punching shear. 2. General shear happens in dense sand or stiff clay. These soils have low compressibility. 3. Local shear happens in loose sand or soft clay. These soils have high compressibility. 4. So local shear failure is linked with high compressibility. Answer is (A).

Explanation

In loose or soft soil, the footing sinks a lot before failure because the soil compresses easily. The failure surface does not reach the ground surface fully, so the failure is local. That is why local shear failure is linked with high compressibility.

Why the other options are wrong

B: High pore pressure is not what decides the failure mode. C: Low porosity means dense soil, which gives general shear failure. D: Low compressibility (dense or stiff soil) gives general shear failure.

Shortcut

Dense or stiff soil means general shear. Loose or soft soil (highly compressible) means local shear.

Common mistake

Mixing up the two: general shear is for low compressibility, local shear is for high compressibility.