含瓦斯冲击倾向性煤体加载破坏电荷感应规律

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

  • 摘要: 为探究含瓦斯冲击倾向性煤体加载破坏过程电荷感应规律及机理,应用自主研制的煤岩电荷监测系统,开展了含瓦斯冲击倾向性煤体加载破坏全过程电荷监测试验。试验结果表明:无瓦斯作用下随着煤的冲击倾向性降低,煤体电荷信号峰值降低,累积电荷事件数减少,单位时间电荷事件数降低,电荷信号向煤体峰值强度后转移;瓦斯作用下,随着瓦斯压力升高,煤的冲击倾向性降低,煤体电荷信号峰值降低,累积电荷事件数和单位时间电荷事件数与瓦斯压力无明显线性关系。研究发现瓦斯作用下冲击倾向性煤体电荷信号呈现“矩形波”特征,信号主频在200 Hz以下,随着瓦斯压力升高,主频信号分量幅值逐渐降低。从煤体内部微裂纹滑移分离和瓦斯运移携带颗粒运动产生自由电荷角度,提出了含瓦斯冲击倾向煤体破坏自由电荷产生机理,一方面,煤体裂纹面附近界面势能超过煤岩界面标准接触界面势垒,导致不同属性带电粒子向不同方向移动,解释了应力突变造成裂纹加速扩展导致电荷信号呈现脉冲簇现象;另一方面,煤岩内部孔隙贯通,瓦斯气体因压力差而流动,Stern-Gouy双电层结构产生流动电荷,流动电荷对煤岩破坏电荷信号贡献附加量,解释了含瓦斯冲击倾向性煤体电荷信号似“矩形波”特征。

     

    Abstract: 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.

     

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