Finite Element Investigation of Base Tilt Effect on Shallow Foundation Collapse

ABSTRACT: The bearing capacity of shallow foundations is classically computed as the sum of three contributions, coming from the soil cohesion, the overburden pressure and the weight of the soil mass mobilized by the collapse mechanism. Each of these contributive terms is then multiplied by several special corrective factors that account for the effect of the shape, depth and tilt of the foundation base, the inclination and eccentricity of the applied load, as well as the slope of the ground. Formulas for such factors have been proposed by several authors and are adopted by many codes of practice, namely Eurocode 7. This paper presents a numerical investigation of the adequacy and range of validity of the corrective factors that apply to foundation base tilt. Tilt angles of 6 and 9 degrees, rigid and flexible footings and small and large strain formulations are combined in a total of 8 finite element analyses of shallow foundation collapse in undrained conditions. It is concluded that for tilt angles above 6o the bearing capacity tends to be overestimated by the classical approach which may lead to estimates that are not on the safe side.