Role of stress, slenderness and foliation on large anisotropic deformations at deep underground excavations

Abstract

High stress concentrations around underground excavations can result in significant damage to deep hard-rock mines. These conditions can be the result of stopping activities, blasting, seismicity, or other mining activities. Large anisotropic deformation and excavation closure, especially under high-stress conditions, are expected if the excavation is located in a foliated or thin-bedded rock mass. In this research, the behaviour of excavations under deep and high-stress conditions was investigated and categorised. The main purpose was to enhance the existing knowledge of managing large anisotropic deformations and to help prepare suitable measures for handling such contingencies. Numerical simulations using the distinct element method (DEM) and model calibration were performed to reproduce the anisotropic deformation of an ore drive based on the collected field data. Then, the roles of key factors (i.e. stress ratio, slenderness ratio, foliation orientation, and foliation considering excavation orientation) on the large deformation and damage depth of the excavations were investigated. This study found that increasing both the stress ratio and slenderness ratio induced linear increases in wall closure and damage depth, whereas increasing the foliation angle first increases the deformation and damage depth and then reduces them both before and after 45°. The wall closure and damage thickness decreased with increasing orientation intercept. The deformation and damage levels were classified based on these factors.

Keywords

• Large anisotropic deformation
• Buckling
• Deep mining
• Slenderness ratio
• Intercept angle
• Foliation orientation