瓦斯抽采下沿空留巷采空区遗煤自燃危险识别研究

Study on the identification of gob coal spontaneous combustion hazard under gob-side entry retaining and gob gas drainage

针对瓦斯抽采下沿空留巷采空区遗煤自燃问题,以试验矿24208工作面为研究背景,采用UDEC4.0和Fluent进行数值模拟,识别了工作面回采过程中顶底板裂隙发育形成机制及演化规律,分析了风量对采空区流场及风排瓦斯的扰动关系,采用示踪气体实测了工作面立体空间的漏风去向及漏风比例。结果表明:当工作面推至65 m时覆岩层达最大程度卸压,垂直裂隙发育高度最大达25 m,有效满足瓦斯抽采;采空区的漏风去向:工作面—采空区—压埋管钻孔、工作面—采空区—沿空留巷、工作面—采空区—邻近层高位钻孔;随风量的增加,采空区氧化带宽度不断扩大且向深部靠拢,下边界整体后移,上隅角瓦斯浓度逐渐下降。

For the gob coal spontaneous combustion problem under gob-side entry retaining and gob gas drainage, formation mechanism and evolution law of roof and floor fracture in the process of 24208 working face of test mine mining were identified by UDEC4.0 and Fluent software for numerical simulation. The influence of air volume and gob air flow field and the gas drainage by ventilation was analyzed. The flow trace and volume of air leakage of the stereo space of working face were measured by using tracer gas. The results show that overburden stratum achieves the maximum range pressure relief when the working face advancing to 65 m and vertical fracture maximum height reaches 25 m, which ef- fectively meet the gas drainage; the passage of gob air leakage as follows, working face-gob-buried hole for gas drainage and working face-gob-gob side entry retaining and working face-gob-adjacent layer high hole; the gob oxidation zone width expands and draws close to the deep and the down boundary integral moves to backward with the increase of the air volume, and then the gas concentration in return corner is gradually decline.