Seismic bearing capacity of rock foundations subjected to seepage by a unilateral piece-wise log-spiral failure mechanism

Abstract

Most of the current studies on the bearing capacity of rock foundations follow the Hoek-Brown (HB) criterion, but all adopt the generalized tangent technique or the multi-tangent approach, which does not reflect the essence of the nonlinear dependence of the Hoek-Brown criterion. Therefore, a modified unilateral failure mechanism is proposed in the paper, using which the bearing capacity of shallow strip footings considering seepage and seismic forces is evaluated. Use of a statics-like approach for seepage condition and a modified pseudo-dynamic method for seismic condition. The comparison with the results of other literature confirms the feasibility and effectiveness of the study in the paper, while the parametric analysis shows that a smaller upper bound solution is yielded based on the failure mechanism proposed in this paper, and the horizontal gradient ratio, the horizontal factor of seismic acceleration, the normalized frequency, the geological strength index, the disturbance coefficient, and the rock type-dependent parameter all have significant effects on the bearing capacity of rock foundations. In addition, the analysis of the working conditions considering both seepage and seismic forces confirmed the dominance of seismic forces. The results of the superposition treatment between different working conditions are inaccurate, which will underestimate the foundation bearing capacity and cause a waste of cost. This paper develops a more accurate method of assessing the bearing capacity of rock foundations and gives a table of coefficients that can be adopted in engineering practice.