Anisotropic and foliated rock masses present particular difficulties in the assessment of pit slope stability. Although many attempts have been made to describe the strength of rock masses that exhibit a preferred orientation of weakness, no general methodology has emerged throughout the literature to simulate anisotropic behaviour in a three-dimensional numerical model of pit slope stability. In order to simulate the effect of the anisotropic shale rock mass on pit slope stability at MMG Limited's (MMG) Century Mine, the Ubiquitous Joint Rock Mass (UJRM) method has been applied. This paper outlines the methodology that was used to assist mine personnel in the management of complex anisotropic slope instability that jeopardised the recovery of 1.8 million tonnes of zinc ore.

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