立井揭煤前测定煤层瓦斯压力的方法与实践

为了解决复杂环境下立井揭煤前煤层瓦斯压力的可靠测定,基于揭煤井筒瓦斯地质特征、煤岩体物理力学性质,应用COMSOL软件模拟揭煤工作面在接近目标煤层时,井筒周围煤岩的地应力分布特征,直观展现了目标煤层中的应力分布结果。模拟结果表明,立井工作面距煤层的垂直距离为7 m时,煤层中会形成一个近似于环形的卸压圈,卸压半径为16 m,因此煤层瓦斯压力测试孔的终孔位置应布置在井筒中心线16 m以外的原始地应力区,以保证测压点瓦斯压力不受揭煤井筒卸压区的影响,令测压结果准确可靠,从而更好地预测煤与瓦斯突出区域的危险性。同时,结合立井揭煤工作面的水文地质特征和井筒严重淋水情况,自主研发并应用了瓦斯测压孔"两堵一注"封孔材料及特定的封孔工艺,进一步保障了封孔质量和瓦斯压力测试结果的可靠性。最后,依据测压结束时测压管内的实际水压情况,对测压结果进行修正,并依据实测瓦斯含量,采用间接法对所测得的瓦斯压力进行验证,实测值在反算得到的瓦斯压力值域内,表明此方法有效可行。

Renovated reliable method for determining the coal seam gas pressure before exposure to the gassy coal seam in vertical shaft coal excavation

The paper intends to propose a renovated method for identifying and determining the reliable coal seam gas pressure before uncovering a gassy coal seam in the shaft sinking face based on the gas geological theory and physico-mechanical properties of the rock mass in such a typical shaft sinking face as the one in Zhaozhuang coal mine.For the research goal,we have simulated the stress distribution status in-situ by using a software named COMSOL in case if the shaft sinking face is close to the target coal seam.The results of our simulated research show that there has been appearing a pressure-releasing circle with its radius of 16 m with its vertical distance of 7 m above the coal seam,which tends to determine the likely gas desorption and the depressed gas situation.In accordance with the above mentioned understanding,the final position of the gas pressure measuring holes in the coalbed should be chosen at a distance of 16 m off the shaft center,i.e.out of the pressure relief area in case the shaft sinking face is at 7 m above the coal seam so as to guarantees a reliable gas pressure measurement.The aforementioned method has been trial-applied in a ventilation shaft sinking engineering practice in the said coal mine,Shanxi province.According to the water pressure we have worked out at the end of the measurement done,we have amended the gas pressure to be adopted.And,then,we have set up a reliable coalbed gas pressure of 1.16 MPa for the coal seam,which has also been used for forecasting the outburst prone of the coal and designing an efficient outburst protection measure for the coal seam opening safely.It has further been verified by using the gas content determining results and methane adsorption parameters for the same hole in accord with the Langmuir equation.Thus,it can be seen that we have self-developed and sealed the gas measuring hole with a specific sealing technique known as "both-end sealing with the middle part grouted" so as to solve a seriously groundwater pushing and flushing problem in the sinking face and ensure reliable gas pressure.Therefore,successftl application of the aforementioned technology in Zhaozhuang coal mine indicates that the renovated method of ours is expected to be feasible and effective in this and other similar engineering fields.