瓦斯抽采过程中煤体低温氧化对煤岩动力灾害的影响

Influence of Low Temperature Oxidation of Coal Body on Dynamic Disasters of Coal and Rock During Coal Seam Gas Extraction

为了探究瓦斯抽采过程中煤岩动力灾害演化过程,了解煤体低温氧化对瓦斯突出影响的作用机理,通过保水法测孔隙率、P波波速测量、瓦斯放散初速度△p和煤岩坚固性系数f来评估瓦斯抽采过程中煤体低温氧化对煤岩动力灾害发生的影响。实验表明:随着煤体氧化温度的升高,煤体质量和P波波速持续降低,煤体内部裂隙逐步发育,孔隙率提高了73.3%;由于煤体内部裂隙发育,煤体结构遭到破坏,坚固性系数随着煤体氧化温度的升高而降低;与煤体坚固性系数相反,由于煤体内部裂隙发育,为瓦斯释放提供了通道,导致瓦斯放散初速度随着煤体氧化温度的升高而增加,并且升高速率逐步增加。煤体的低温氧化过程会导致煤体强度降低,瓦斯涌出压力增加,引发瓦斯突出综合预测指标K值大幅增加,煤岩动力灾害发生可能性也随着增加。

In order to study the evolution process of coal and rock dynamic disaster during gas drainage and to understand the mechanism of low-temperature oxidation of coal body, the influence of low temperature oxidation on coal rock power disasters in gas extraction was evaluated by means of water retention measuring porosity method, P wave velocity measurement, initial velocity of gas release and strength coefficient of coal rock. The results show that with the increase of the oxidation temperature of coal,the coal quality and the velocity of P-wave continuously decrease, the internal fractures develop gradually and the porosity increases by 73.3%; the structure of coal body is destroyed by the development of coal, and the firmness coefficient decreases with the increase of the oxidation temperature of the coal body; on the contrary, the fracture of the coal body provides the channel for the gas release, contrary to the solid coefficient of the coal body. The initial velocity of the gas dissipation with the coal oxidation temperature increases, and the rate of increase gradually increases. The low temperature oxidation process of coal body will lead to the decrease of coal body strength and the increase of gas emission pressure, which will lead to a significant increase of the comprehensive forecast index K of gas outburst and the possibility of coal rock dynamic disaster.