Terzaghi’s Bearing Capacity – Key Assumptions in Classical Analysis Which of the following are assumptions in Terzaghi’s classical bearing capacity theory for shallow foundations on soil?

Introduction / Context:
Terzaghi’s bearing capacity theory remains a cornerstone for preliminary design of shallow footings. It uses an idealized soil model and failure mechanism to derive ultimate bearing capacity in terms of c, φ, and γ with bearing capacity factors N_c, N_q, and N_γ.

Given Data / Assumptions:

• Shallow, strip footing on weighty soil mass.
• Soil treated as homogeneous and isotropic near the footing.
• Failure mechanism with defined plastic and elastic regions.

Concept / Approach:

In Terzaghi’s mechanism, a central active wedge under the footing is bounded by planes at angles ψ = φ from the horizontal, flanked by passive Rankine zones, with radial shear zones outside. The failure surface is assumed not to extend above the footing base. These idealizations enable closed-form expressions for ultimate capacity. While actual soils may deviate, the theory provides practical baseline values modified by shape, depth, and load inclination factors.

Step-by-Step Solution:

Verification / Alternative check:

Modern formulations (e.g., Meyerhof, Hansen, Vesic) adjust Terzaghi’s assumptions but keep the core mechanism concept, confirming the statements’ relevance to the classical approach.

Why Other Options Are Wrong:

Choosing any single item omits other essential assumptions; 'None of the above' is incorrect.

Common Pitfalls:

Applying Terzaghi’s theory without correction factors; ignoring groundwater and footing shape effects.

Final Answer:

All of the above