Net Safe Bearing Capacity from Ultimate Bearing Capacity A shallow foundation bears on soil with ultimate bearing capacity qu = 300 kN/m^2. Depth of foundation Df = 1 m, unit weight of soil γ = 20 kN/m^3. Using a factor of safety FS = 2.5, compute the net safe bearing capacity.

Introduction / Context:
Bearing capacity terms distinguish between gross and net values. Design often uses net safe bearing capacity (qns), which subtracts the overburden at foundation level and divides by a factor of safety to guard against shear failure.

Given Data / Assumptions:

• Ultimate bearing capacity (gross): qu = 300 kN/m^2.
• Depth Df = 1 m; unit weight γ = 20 kN/m^3.
• Factor of safety FS = 2.5.

Concept / Approach:

Net ultimate bearing capacity: qnu = qu − γ * Df. Net safe bearing capacity: qns = qnu / FS. This removes the contribution of overburden pressure and applies safety margin to the shear failure criterion.

Step-by-Step Solution:

Verification / Alternative check:

Cross-check units and arithmetic; results are consistent with typical values for medium soil strengths.

Why Other Options Are Wrong:

• 100 and 100.5 kN/m^2: Do not match the net–ultimate then divide by FS sequence.
• 800 kN/m^2: Exceeds ultimate capacity; impossible.

Common Pitfalls:

Dividing gross ultimate by FS without subtracting overburden; confusing net safe with gross safe capacity.

Final Answer:

112 kN/m^2