Characteristics of Strata Behaviors and Roof Control for Longwall Faces in Deep Mining

According to the principle of strata control around longwall face, the formulas for judging caved zone and for calculating the subsidence of main roof in fractured zone at the contacting place with goaf dirt, and the relation between the front abutment pressure and mining depth, the effect of mining depth on the different parameters of strata behaviors of longwall face was analysed, and verified by field measurements. Based on the change of rock properties with mining depth increasing, the probable roof collapse in longwall faces in deep mining was discussed and the countermeasures of roof control were suggested. It is concluded that the effect of mining depth on strata behaviors of longwall face is not obvious in supporting, while the rib spalling is aggravated with mining depth increasing. The surrounding rock in the deep gradually becomes fragmentary and rock strength drops to some extent, the prevention of roof collapse with cavity by leaking should be paid special attention to and roof be shielded well in deep mining.