Variation characteristics of capacity dimension D_f with microseismicity in deep mining

Based on complex geological conditions in Huize Lead Zinc Mine,a digital 24-channel microseismic monitoring system was established to monitor microseismic events in deep mining.In the monitoring period,microseismic parameters were recorded such as b values,magnitude and the number of microseismic events.The relation of D_f =2b was deduced between capacity dimension D_f and b values.After analyzing the monitoring data,the changes of D_f values with time and stope collapse were determined.The results show that rockmass failure is closely related with D_f values.With the change of mining disturbance,the stress concentration of local rockmass induces crack compaction,initiation and propagation,meantime the D_f values increase and then stay relatively quiet,meaning that the crack roughness of rockmass is increasing.Once dynamic disasters are caused by rock mass failure,the D_f values abruptly decrease,which means that the crack roughness of rockmass reduces and it leads to the acceleration of rockmass instability.Combining with site examination,it is concluded that the probability of rock failure increases with decreasing D_f values.