Experimental Study On Influence Of Gas Occurrence On Dynamic Mechanical Properties Of Coal

The essential description of coal and gas dynamic disasters in mines is the severe damage and destruction of coal under the condition of high gas occurrence under the action of mining dynamic disturbance.Because of the increase of underground coal mining depth,the gas rich state of coal and rock mass in large buried coal seam is becoming increasingly serious,the existence of gas makes the dynamic mechanical properties of gas bearing coal completely different from those without gas,so it is of great significance to understand the dynamic mechanical characteristics of coal bearing coal and rock through the impact dynamic experiment and it is also the urgent work to be carried out in the field of coal and rock mechanics.This paper selects raw coal samples from 11426 working face of Xie Qiao mine in Huainan mining area as an example,a study on the influence of gas occurrence on the dynamic mechanical properties of coal is carried out by using the dynamic mechanical properties experiment of gas containing coal and theoretical analysis of fracture mechanics.The research contents and achievements of the thesis are as follows:(1)Using the dynamic disturbance SHPB device containing gas coal to carry out the SHPB impact test of the gas containing coal(OMPa,0.5MPa,1MPa,1.5MPa)under different gas pressure.The experimental results show that with the increase of air pressure,the transmission wave gradually decreases,and the reflected wave increases gradually;with the increase of air pressure,the average dynamic strength,the secant modulus and the energy utilization ratio of the coal samples decrease,the dynamic stress growth factor increases,and the percentage of the small size debris increases.(2)Based on the theory of fracture mechanics and the principle of effective stress superposition,a mathematical model of stress intensity factor considering gas pressure is established,through the calculation and analysis of a given constant:The type I stress intensity factor of open crack increases with the increase of gas pressure and gas desorption rate and decreases with the increase of crack inclination angle;The open type crack type II stress intensity factor has nothing to do with gas desorption coefficient and gas occurrence pressure;With the increase of gas pressure the crack initiation angle and crack initiation strength decrease.The theoretical analysis of the fracture mechanics of gas coal proves the correctness of the experimental results.The theoretical analysis provides a basic theoretical basis for understanding how the gas occurrence changes the dynamic mechanical properties of coal and provides a theoretical basis for the rapid mining and disaster prevention and control of the deep gas bearing coal seam.