Foundations – Situations where pile foundations are preferred Pile foundations are generally provided when the soil at shallow depth is:

Introduction / Context:
Pile foundations transfer loads to deeper, stronger strata or develop capacity through skin friction and end bearing. They are chosen when shallow foundations would be unsafe or uneconomical due to soil conditions near the surface.

Given Data / Assumptions:

• Site with problematic near-surface soils.
• Building loads that require reliable settlements and capacity.
• Access for piling equipment is feasible.

Concept / Approach:
Compressible clays and organic silts cause excessive settlement under shallow footings. Water-logged soils complicate excavation and reduce bearing due to reduced effective stress. Made-up ground may be heterogeneous and still consolidating. In all these cases, piles bypass problematic strata to competent layers or mobilize friction over length.

Step-by-Step Solution:
Assess shallow strata: if weak/compressible → shallow footings unsuitable.Consider groundwater: dewatering may be impractical; piles minimize open excavation.Consider fill: variability and ongoing settlement favour deep foundations.Conclude that all listed conditions justify piles.

Verification / Alternative check:
Geotechnical design charts and codes recommend piles for low near-surface bearing capacity, high settlement potential, or construction difficulties in wet conditions.

Why Other Options Are Wrong:

• a–c are each true triggers; thus “All of the above” is correct.
• “None of these” contradicts standard deep foundation selection criteria.

Common Pitfalls:
Choosing piles without a subsurface investigation; always confirm target bearing layer depth and capacity, and evaluate negative skin friction if fills or groundwater changes are expected.

Final Answer:
All of the above