Theoretical Bearing Capacity of Very Shallow Footings

The bearing capacities of very shallow, perfectly smooth strip and circular footings are obtained by integration of the equations of plastic equilibrium of soils. The equations are integrated numerically by a finite difference approximation based on the method of characteristics. Calculations are carried out for cohesionless soils with angles of internal friction of 30○ and 40○. The results are linearized to obtain bearing capacity factors Nγ and Nq and shape factors for a circular footing. The increase of the calculated bearing capacity with depth of burial is sufficiently large to indicate that the small footing settlement prior to failure is a significant factor in the large discrepancies between theoretical and experimentally observed bearing capacities.