Limit load space of rigid strip footing on cohesive-frictional soil subjected to eccentrically inclined loads

Abstract

In geotechnical engineering, the stability of strip footings under eccentrically inclined coupled loads is a major concern. The objective of this paper was to estimate the ultimate bearing capacity of a rigid strip footing, subjected to eccentrically inclined loads resting on cohesive-frictional soil, using the rigid plastic finite element method (RPFEM). In the numerical analysis, an interface element was introduced to properly evaluate the interaction between the footing base and the soil. The footing base was assumed to be rigid and rough, as it most often is in reality. Focus was placed on the effect of the soil properties (cohesive strength c, internal friction angle ϕ, and unit self-weight γ) and footing width B on the loading planes of the V-H-M limit load space (vertical load-horizontal load-moment) in order to consider the uniqueness of this limit load space. In particular, the effect of the two directions of the horizontal load, namely, positive and negative horizontal loads, on the V-H-M limit load space was clarified. The numerical results of the RPFEM showed that the negative horizontal load had a positive effect on supporting a higher bearing capacity than the positive horizontal load in the presence of a small eccentricity length. However, the results also showed a negligible effect on the bearing capacity for both directions of the horizontal load in the presence of a large eccentricity length. New equations were proposed to determine the V-H-M limit load space, predicted as functions of c/γB and ϕ, by taking into account the direction of the horizontal load. The applicability of the V-H-M limit load space was widely examined for several loading paths with different prescribed loads for V, H, and M. Consequently, the limit load space of the strip footing was clearly found to be unique for each value of c/γB and ϕ.