Uncertainty in Bearing Capacity of Sands

Bearing capacity predictions for surface footings on sand based on modifications of Terzaghi's superposition method are partly empirical and partly theoretical. Based on currently available data for surface footings on sand, these predictions are compared with statistical analyses. For small uncertainty in soil properties, coefficients of variation of bearing capacity for cohesionless soil without surcharge range from 20% to 30%. As uncertainty in soil properties is introduced, uncertainty in bearing capacity rises rapidly. Quantified expressions of uncertainty are derived and illustrated by example. These analyses are used to identify sources of uncertainty.