Foundation support basics: A foundation transfers load to which supporting medium(s)? Choose the most accurate statement.

Introduction / Context:

Foundations are structural elements that transmit loads from the superstructure to the ground. Clarity in terminology helps avoid design misunderstandings: ‘‘subgrade’’ and ‘‘foundation soil’’ are commonly used to denote the supporting ground strata beneath the foundation element.

Given Data / Assumptions:

• General building foundation (shallow or deep).
• Soil or rock as the load-bearing medium.
• Standard geotechnical terminology.

Concept / Approach:

The foundation element (footing, mat, pile cap, etc.) distributes loads to the underlying geomaterial. That supporting medium is the ‘‘subgrade’’ or ‘‘foundation soil/rock.’’ Saying a foundation ‘‘rests on the base of the foundation’’ is tautological and not physically meaningful; the foundation itself bears on the soil or rock.

Step-by-Step Solution:

Verification / Alternative check:

Soil–structure interaction models and bearing capacity equations (e.g., Terzaghi, Meyerhof) explicitly treat the underlying soil/rock as the resisting medium.

Why Other Options Are Wrong:

• Base of the foundation: Not a supporting medium; it is the foundation's underside surface.
• Bedrock only: Not all foundations bear on rock; many bear on competent soils.

Common Pitfalls:

• Confusing structural parts (footing base) with geotechnical support (soil/subgrade).

Final Answer:

both (b) and (c)