Pile Foundations MCQ with answer and solution

Concept

Applicability of dynamic pile formulae in cohesive soils

Formula

NONE

Step-by-step solution

1. Dynamic pile driving formulae are based on the principle of conservation of energy during pile driving. 2. In clayey soils, dynamic driving causes remolding and high dynamic pore water pressure development, making dynamic resistance significantly different from static load capacity. 3. Therefore, dynamic formulae cannot be used to reliably obtain load carrying capacity in hard clays. Answer: C

Explanation

Dynamic pile formulas rely on the kinetic energy imparted during driving, which works well for coarse-grained soils. In hard clays, pile driving generates temporary pore water pressures and soil remoulding, making driving resistance significantly different from long-term load capacity. Consequently, static load tests or static formulas must be used instead for cohesive soils.

Why the other options are wrong

A) Dynamic formulae can be used in uniform fine sand as pore water pressures dissipate relatively quickly. B) Dynamic formulae are suitable for free draining sands due to rapid pressure dissipation. D) Option C is the correct choice.

Shortcut

Dynamic formulae fail in cohesive soils like hard clays due to remolding and pore pressure.

Common mistake

Assuming dynamic driving formulas can be applied to cohesive soils like hard clays where pore pressure affects resistance.