Geomechanics and control of soft mine floors and sides (GEOSOFT) : final report

GEOSOFT researched soft coal mine floor and side behaviour to develop enhanced design and construction solutions. Longwall mining on soft floor rocks is difficult and requires safe efficient techniques to extract coal at economically viable rates. The Geosoft studies have led to guidelines from the design and the optimisation of powered supports operating on soft rock floors. These guidelines have been achieved by laboratory testing of an instrumented powered support on a purposely designed hydraulic cushion to simulate soft floor behaviour; then monitoring in-situ underground and results from validated numerical modelling. Rockbolted coal mine roadways need to be designed and adequately supported to allow safe and efficient longwall coal production. Numerical modelling is a powerful tool for aiding design and improvements have been made in its use and application. Improvements in mesh, polyurethane resin products and placement techniques, and better rib anchoring systems have been achieved to improve rib support. Floor heave is primarily managed by removal and more pro-active management practices have optimised the dinting process and rib stability. Understanding of closed support design where strata deformation can subject tunnel linings to long term loading has been improved. Laboratory testing of shotcrete creep properties allowed appropriate constitutive models to be developed for numerical models for more accurate simulation of this support method. Different floor support designs were modelled indicating that curved inverts provided the lower maintenance solutions resisting cracking better than slab inverts.