Ultimate bearing capacity of strip footings above rectangular voids in Hoek-Brown rock masses

Abstract

The bearing capacity of a rigid strip footing placed on a rock mass with a rectangular void is determined using the upper bound finite element limit analysis in conjunction with the adaptive mesh refinement technique. The rock mass is assumed to obey the generalized Hoek-Brown (GHB) yield criterion. The optimization model is solved by using the second order cone and power cone programming, which enables the GHB yield criterion to be used in its native form, without the need for smoothing. Based on the method, the reduction factor is calculated and presented in a series of dimensionless charts for design purpose. The influence of material parameters (such as the geological strength index GSI, material constant mi and intact rock strength σci) and geometric parameters (including the height and width of the void, as well as the horizontal and vertical distance between the void and the strip footing) on the reduction factor is considered. Typical failure patterns are discussed in detail to offer a deeper explanation of how the voids affect the bearing capacity of strip footing.