Deformation Behaviour of Rock Slopes on Pre-Existing Shear Surfaces

The deformation behaviour of a rock slope prior to collapse is inherently related to the failure mechanism, strength of the defects controlling the failure mechanism, and in some cases is related to the rock mass strength. This paper presents results of analysis of a selection of rock slopes whose deformation behaviour has been influenced by defects that have experienced significant shearing. The rupture surfaces of these slope failures have experienced large deformation due to either regional folding, stress relief or previous instability. Examination is made of the relationship between normal effective stress acting on the rupture surface, rock mass dilation, over-riding of defect asperities and shearing or crushing of asperities. These factors are considered in the context of slope deformation behaviour and discussion is presented on their influence.