Interpreting hanging wall deformation in mines

Abstract

The deformation behaviour of a hanging wall will follow distinct stages related to the changing material properties of the overall rock mass. This changing rock mass behaviour can be due to increasing underground opening size, blasting, changing stress conditions, as well as increasing opening exposure time. This paper examines the deformation behaviour of stope hanging walls due to changing opening geometry. The effect of time on deformation is observed, but is difficult to interpret. Field deformation data are presented from open stope hanging walls at Mount Isa Mine in Australia. Changing deformation response is related to increased opening spans recorded for two stopes. Some modelling studies are also presented which relate modelled elastic deformation near an opening surface to the opening geometry. Based on numerical modelling methods, it is difficult to predict the deformation of a hanging wall surface. This paper presents an approach for interpreting the rock mass behaviour based on the recorded deformation response of the hanging wall to continued mining.