Bearing Capacity of Soil MCQ with answer and solution

Concept

General shear failure occurs in dense soils and stiff clays under shallow foundations, marked by a clear slip surface, heave of the ground surface, and a sudden ultimate bearing capacity.

Step-by-step solution

1. Identify the soil type and condition given in the problem: very dense sand. 2. Recall Terzaghi's classification of shear failures in foundation soils: General shear failure, Local shear failure, and Punching shear failure. 3. Associate dense sands and stiff clays with general shear failure (relative density Dr > 70% or angle of internal friction φ > 36°). 4. Conclude that option (C) is the correct answer.

Explanation

According to Terzaghi's bearing capacity theory, shallow foundations on dense or stiff soils (like very dense sand or stiff clay) undergo general shear failure. This type of failure is characterized by a well-defined failure surface extending up to the ground surface, accompanied by bulging of the ground surface adjacent to the foundation and a sudden, catastrophic collapse.

Why the other options are wrong

A: Punching shear failure occurs in very loose sands or soft clays, and in deep foundations. B: Local shear failure occurs in medium dense sands or firm clays. D: Intermediate failure is not one of Terzaghi's primary classical shear failure modes for shallow foundations.

Shortcut

Remember the dense-general rule: Dense/Stiff soil = General shear failure; Loose/Soft soil = Punching or Local shear failure.

Common mistake

Confusing dense sand with loose sand, which would lead to punching or local shear failure.