Numerical analysis of fault-slip behaviour in longwall mining using linear slip weakening law

Coal burst induced by fault-slip in longwall mining can adversely influence underground mining activities. This paper analyses the source mechanisms of fault-slip behaviour using a numerical fast Lagrangian analysis of continua in three dimensions (FLAC(3D)) model. The fault was simulated by the build in zero-thickness interface elements. The post failure process of fault-slip was studied using the linear slip weakening law which was implemented in a user-defined FISH program. The numerical results showed that the fault-slip presented significantly different trends at different positions along the fault. Seismic events mainly occurred at the fault area where the normal stresses reduced drastically. Few seismic events occurred when the distance between the longwall face and the fault was less than 20 m. For the parameters of the linear slip weakening law, the influence of the dynamic friction and the critical slip distance were analysed. These two parameters have significant impact on the occurrence of seismic events and the source parameters of fault-slip. The parametric study showed that fault-slip with around 0.1 m of critical slip distance was able to release larger seismic energy than fault-slip with both less and greater than 0.1 m of critical slip distance. The outcomes of this paper help to better understand the seismic fault-slip process in longwall mining and the influence of the critical parameters of the linear slip weakening law on seismic fault-slip behaviour.