Electric charge induction law of coal rock containing gas with bursting tendency during loading failure process

In order to explore the electric charge induction law and its mechanism during the loading failure process of coal rock containing gas with bursting tendency,the electric charge monitoring experiment of the whole loading and failure process of coal rock containing gas with bursting tendency was carried out by using the self-developed coal rock electric charge monitoring system. The results show that with the coal rock bursting tendency decrease under the action of gas-free,the peak value of coal rock electric charge signal decreases, the number of cumulative electric charge events decreases,the number of electric charge events per unit time decreases,and the charge signal transfers to the post-peak strength of coal. Under the action of gas,the bursting tendency of coal rock decreases,accompanied by the increase of gas pressure,the peak value of coal charge signal decreases,and the number of cumulative charge events and the number of charge events per unit time has no obvious linear relationship. It is found that the charge signal of coal with bursting tendency under the action of gas presents the characteristics of “ rectangular wave”,and the main frequency of the signal is below 200 Hz. With the increase of gas pressure,the amplitude of the main frequency signal component decreases gradually. From the standpoint of free charge generated by slip separation of micro-cracks in coal body and movement of particles carried by gas migration,the generation mechanism of free electric charge in coal rock containing gas with bursting tendency is put forward. On the one hand,the interface potential energy near the crack surface of coal rock exceeds the standard interface barrier of coal rock interface,which results in the movement of elec- tric charge particles with different attributes towards different directions and explains the acceleration propagation of crack caused by stress mutation leads to the phenomenon of impulse clusters in electric charge signals. On the other hand,the pore in coal rock is interconnected,and the gas flows under differential pressure. Stern-Gouy electric double layer structure produces flowing electric charge,the flowing electric charge contributes additional quantity to the charge signal of coal rock,which explains the quasi-rectangular wave characteristics of electric charge signal of coal rock con- taining gas with bursting tendency. The results provide basic information for the electric charge inductive method moni- toring and early warning of rock burst and gas outburst compound dynamic disaster.