Study on mechanical properties and acoustic emission characteristics of coal at different gas pressure

In order to study the mechanism of gassy coal-rock complex dynamic disaster,based on the analysis of primary porosity and fractures of the coal samples of the Sanjiaohe colliery,Tunliu colliery and the 10th Mine of Pingdingshan coal group,this paper selected the coal samples of Pingdingshan as subject.Then,by using the self-developed device which contained the gas and coal-rock samples in deformation and failure under load and DS-5 full information acoustic emission signal analyzer,the experiment analyzed the mechanical properties and acoustic emission characteristics of coal-rock under different gas pressure.It also analysed the evolution of acoustic emission count,cumulative count,energy,and accumulated energy under different gas pressure.The result shows that:with the increase of gas pressure (0～2 MPa),the peak intensity and elastic modulus of coal samples decrease,but the Poisson's ratio increases.The compressive strength decreases by 22.61%,the elastic modulus decreases by 23.97% and Poisson's ratio increases by 33.67%.The acoustic emission of coal samples under different gas pressure have experienced four stages: stationary period,active period,speed-up movement period and residual motion period.The coal samples’acoustic emission cumulative count and accumulated energy decreases with increasing gas pressure,and the acoustic emission cumulative count decreases by 32% and the cumulative energy declines by 25.32%.The research results are helpful to find out the meso-mechanism of coal and and provide the basis for predicting the failure of coal and rock mass.