Analytical evaluation of the effect of failure mechanisms on the bearing capacity factor Nγ for smooth strip footings

ABSTRACT This paper describes an analytical approach to investigating the role of failure mechanism in the bearing capacity of a smooth strip footing located on a - - soil. The approach combines the plane strain equilibrium condition and Mohr-Coulomb failure criterion to obtain the stress distribution along a translational, rotational and composite failure path. It is shown that the exact solutions for cohesion factor and surcharge factor for a - - soil do not require the superposition assumption and that both these factors are path-independent. A general closed-form path-dependent expression for the soil weight factor is also derived in terms of internal friction angle of the soil and the geometry of the failure path. The application of proposed expression on two-line and three-line failure modes as well as the well-known Hill mechanism are evaluated and discussed. Due to the overestimation of the soil weight factor by two-line and three-line modes, and by Hill mechanism, geometric modifications on the failure paths are proposed. The proposed mechanism and its bearing capacity are verified using the method of the stress characteristics. The effect of a non-associated flow rule on the reduction of the soil weight factor is also investigated quantitatively.