Study on propagation laws of shock wave in coal-rock mass under the effect of gas outburst

The formation reasons of shock wave were revealed through over forty simulation experiments for coal and gas outburst.On this basis,a one-dimensional propagation model of shock wave in coal-rock mass was developed.According to the stress wave theory,main propagation laws of shock wave were analyzed as follows:① When a shock wave propagation on the coal interface,the stress value of the shock wave reflected into the coal-rock mass is twice that of the incident shock wave;② When a shock wave propagation in a single layered coal,it will be reflected on the free interface at both ends of the single layered coal,and tremendous tensile stress will be generated,which will tear the single layered coal into several thinner laminas;③ When a shock wave propagation to the interface in the assembled medium of tectonic coal and rock(hard coal),strong assembled and reflection will be created at the interface with reverse loading of the reflected wave and strong compressing in the coal.When the strength exceeds that of soft coal,the soft coal will be fractured and damaged.In terms of the whole outburst process,tensile stress plays a major role in damaging the coal.