Anisotropic rock mass behaviour in large deformation ground at CSA mine

Abstract

This paper summarises key findings from a 39-month study at CSA Mine on factors controlling anisotropic ground behaviour in sub-level open stope (SLOS) access tunnels at depths of 1500 m – 1700 m. The aim was to understand factors controlling high displacement ground behaviour through numerical and empirical back analysis at 45 damage sites over a 39-month period. It was found that excavation orientation, rock mass matrix and foliation strength, and stress path are key parameters influencing tunnel damage and convergence at CSA Mine. Tunnels driven parallel to foliation (i.e., along strike), experienced much higher levels of damage than those driven perpendicular to foliation. Drives at intermediate angles experience varying levels of damage, depending on rock mass strength and stress. The stress path induced by mining was found to significantly affect both the initiation and progression of damage in both tunnels and raises.