Geotechnical and Foundation Engineering Flashcards

For a strip footing on saturated clay under undrained (φ = 0) conditions, the Prandtl/Meyerhof bearing capacity factor Nc is:

Answer: 5.14

Nc = π + 2 ≈ 5.14 for φ = 0; Terzaghi's original value is 5.7.

A footing of width B carries a load with eccentricity e in one direction. Meyerhof's effective width used in bearing capacity calculations is:

Answer: B - 2e

Meyerhof's method uses B' = B - 2e so the load acts at the center of the reduced area.

To avoid tension (loss of contact) beneath a rectangular footing under one-way eccentric loading, the eccentricity must not exceed:

Answer: B/6

Keeping e ≤ B/6 keeps the resultant within the kern and the minimum bearing pressure non-negative.

When the groundwater table rises to the base of a shallow footing in sand, how should the Nγ term of the bearing capacity equation be modified?

Answer: Replace γ with the buoyant unit weight γ' in the Nγ term

Soil below the base is submerged, so the effective (buoyant) unit weight is used in the Nγ term.

Which method is commonly used to estimate immediate settlement of shallow foundations on sand using CPT cone resistance and a strain influence factor diagram?

Answer: Schmertmann's method

Schmertmann's method integrates a strain influence factor with modulus derived from CPT qc.

What factor of safety is typically applied to the ultimate bearing capacity of shallow foundations in allowable stress design?

Answer: 3.0

A factor of safety of about 3 is customary to account for uncertainty and limit settlement.

A fully compensated mat foundation is designed so that:

Answer: The weight of excavated soil approximately equals the building load, so net added stress is near zero

Removing soil equal in weight to the structure leaves little net stress increase, minimizing settlement.