Determining Bearing Failure Modes of Jointed Rock Foundations Subjected to the Load of Strip Footings

Abstract

The main prerequisite for choosing the best method of obtaining the ultimate bearing capacity of soils or rock masses is determining the probable failure mode that can occur beneath the footing. Most available methods for determining the bearing capacity of rock masses are based on general shear failure of the rock mass. But depending on the properties of the intact rock and the joint sets, other types of failure modes including local or punching shear failure may occur. In such conditions, using relations which are based on the general shear failure is not sufficiently precise. In this study, distinct element method was applied for performing wide sensitivity analyses on different intact rock and the joint sets characteristics; the range of occurrence of failure modes was investigated. Three types of failure modes including general shear failure, local shear failure, and punching shear failure were considered under the vertical load of a strip footing. Two perpendicular joint sets were considered for the jointed rock mass and different orientation angles and spacing were also taken into account for the joint sets. The obtained results showed that the shear strength properties of the intact rock and the joint sets, the elastic modulus of the intact rock and the orientation angle and spacing of the joints have a considerable effect on the mode of failure, while the normal and shear stiffness of the joint sets do not play an important role in the failure mode.