Failure mechanisms and calculation of bearing capacity of a strip footing on soil considering joined influences of cohesion, surcharge and gravity

A numerical method for bearing capacity analysis by the upper bound theorem is presented. Based on the well-known Mohr-Coulomb failure criterion and the associated flow rule, the present method establishes kinematically admissible velocity field within assumed failure mechanism and a work-energy balance equation for determination of the ultimate bearing capacity of a strip footing by minimization. Since the bearing capacity is due to the interaction between (or joined influence of) friction of angle φ, cohesion c, surcharge load q and unit weight of soil γ, a general equation of bearing capacity considering the interaction is derived. Three bearing capacity factors considering the cohesion, surcharge and weight of soil are obtained using two approaches: (a) considering the joined influence and (b) separate calculation. The critical failure mechanisms for the two approaches are obtained and compared. The computed values of the three factors using the two approaches are compared to those publishe d in the literatures. Agreement and differences are discussed.Department of Civil and Environmental Engineerin