煤与瓦斯突出瓦斯压力临界值的研究

On the critical value of gas pressure of coal and gas outburst

煤与瓦斯突出是煤矿主要瓦斯灾害事故类型之一。目前,国内关于煤与瓦斯突出预测的方法主要是根据瓦斯动力现象和基于煤层瓦斯压力、破坏类型、坚固性系数与瓦斯放散初速度的四参数法。对于发生过瓦斯动力现象的矿井以瓦斯动力现象的特征作为评判的依据,对于没有发生过瓦斯动力现象的情况以四参数法为主。四参数法规定,4个参数均超过各自的临界值才能定为突出煤层,瓦斯压力的临界值定为0.74 MPa。而实际情况是,瓦斯压力小于0.74 MPa的煤层也曾多次发生突出。用可压缩流体力学的观点分析了突出机理,采用多相连续介质力学中的应力分析法建立了瓦斯压力临界值的理论计算式,根据矿井瓦斯赋存规律分析了所得结果的合理性,并给出了有关参数(特别是煤层内摩擦角)的计算方法。案例分析表明,所得结果符合实际情况,同时给出了进一步的研究方向。

The paper is inclined to provide a theoretical account for the coal and gas outburst, for it is one of the key reasons to lead to the coal mine burst disasters. It is known that for the time being, the main method for predicting the outbursts of coal mine is the one based on the analysis of the gas dynamic behaviors and the so-called four parameters （i. e. the gas pressure of the coal seam, the crushed type of coal, the coal hardiness coefficient and the index of initial velocity of diffusion of coal gas） at home. In our opinion, the former （i. e. that based on the gas dynamic phenomena） is suitable for the coal mines wherein the gas dynamic phenomena occur and the latter for those in which no gas dynamic phenomena cropping up. Whereas the four-parameter method claims that it is necessary to classify the coal seam into outburst ones and silent ones merely dependent of whether all of the four parameters exceed their alternative critical values. The so-called critical value of the gas pressure of coal seams is thought of to be 0.74 MPa. However, the coal production experience shows that the outbursts are likely to occur even when the gas pressure is less than 0.74 MPa. It is just for this reason that we have made an ac- count of the mechanism of the outburst from the point of view of com- pressible fluid dynamics and the theoretical formula for the critical gas pressure with the help of the stress analysis of multi-phase continuum mechanics. The final result can be summarized as, wherein, p is the gas pressure of the coal seam, Pl is the air pressure of excavation space, is the average density of the surface-level rocks, g is the gravity acceleration, h is the depth of the coal seam, and q is the angle of internal friction of the coal seam. The reasonableness of the formula is checked with some common documents in the field of gas control of coal mines. Methods for determining the parameters, especially one for are giv en. And, finally, our case analysis reveals that the formula is in per-fect accordance with the practice. And, finally, we have also pointed out further research to be done in the future.