How is allowable bearing pressure computed?

How is allowable bearing pressure computed?

• A. Allowable bearing pressure = Ultimate bearing capacity multiplied by safety factor.
• B. Allowable bearing pressure = Ultimate bearing capacity minus a fixed reduction.
• C. Allowable bearing pressure = Soil bearing capacity divided by water table height.
• D. Allowable bearing pressure = Ultimate bearing capacity divided by safety factor.

Answer: (D)

Designing allowable bearing pressure starts from the soil’s ultimate bearing capacity—the maximum pressure the soil can carry before failure. To ensure safety, this ultimate capacity is divided by a factor of safety, yielding the allowable (safe) bearing pressure—the pressure you can actually design for without risking failure. So, the correct relation is allowable bearing pressure = ultimate bearing capacity divided by the safety factor. For example, with an ultimate capacity of 1800 kPa and a safety factor of 2, the allowable pressure would be 900 kPa. This approach keeps the design within the soil’s safe limits; multiplying by the safety factor would inflate support capacity, subtracting a fixed amount isn’t the standard method for bearing capacity design, and dividing by groundwater height isn’t related to bearing capacity calculations.

Designing allowable bearing pressure starts from the soil’s ultimate bearing capacity—the maximum pressure the soil can carry before failure. To ensure safety, this ultimate capacity is divided by a factor of safety, yielding the allowable (safe) bearing pressure—the pressure you can actually design for without risking failure. So, the correct relation is allowable bearing pressure = ultimate bearing capacity divided by the safety factor. For example, with an ultimate capacity of 1800 kPa and a safety factor of 2, the allowable pressure would be 900 kPa. This approach keeps the design within the soil’s safe limits; multiplying by the safety factor would inflate support capacity, subtracting a fixed amount isn’t the standard method for bearing capacity design, and dividing by groundwater height isn’t related to bearing capacity calculations.