大直径双钻孔强化抽采瓦斯效应及效果分析

为探讨大直径双钻孔强化抽采瓦斯效应，以山西石泉煤矿30110回采工作面为对象，利用RFPA2D-Gas建立不同直径单孔和双?350 mm钻孔的数值模型，分析了钻孔周围煤体的应力分布、损伤破裂、透气性演化及瓦斯运移规律，并对双?350 mm钻孔抽采效果进行了考察验证。模拟结果表明:?100、?250、?350和双?350 mm钻孔卸压半径分别为0.25、0.9、1.2、2.2 m；?250、?350和双?350 mm钻孔周边煤体损伤破坏以蝴蝶展翅形态向钻孔上方两侧延展；双?350 mm钻孔上方1.5 m处煤体透气性系数可由0.25 m2/(MPa2·d)增至240 m2/(MPa2·d)；瓦斯运移速率随钻孔直径增加而增大，在抽采过程中逐渐降低，当煤体破裂时会有一定幅度增加。现场考察结果显示双?350 mm钻孔可利用钻孔塌裂强化抽采效果，抽采半径为2 m，流量可达?100 mm钻孔的21倍，抽采总量为?100 mm钻孔的10倍以上，甚至可达到40倍。 

Mechanism and effect analysis of enhanced gas drainage with large diameter double boreholes

To study the mechanism of enhanced gas drainage with large diameter double boreholes, numerical models of single holes with different diameters and double ?350 mm holes were established by using the RFPA2D-Gas software in working face 30110 of Shiquan Coal Mine, Shanxi Province. Stress distribution, damage and fracture, gas permeability evolution and gas migration law of the coal around the hole were analyzed, and then the extraction effect of double ?350 mm holes was investigated. Simulation results show that the pressure relief radii of the ?100 mm, ?250 mm, ?350 mm and double ?350 mm holes are 0.25 m, 0.9 m, 1.2 m and 2.2 m, respectively. The coal damage extends to the upper left and upper right around the holes of ?250 mm, ?350 mm and double ?350 mm, and the final fracture shape is like spreading wings of a butterfly. The permeability coefficient of the coal at 1.5 m above the double ?350 mm holes can increase from 0.25 m2/(MPa2·d) to 240 m2/(MPa2·d). The gas migration rate increases with the increase of hole diameter, and gradually decreases in the drainage. However, when the coal around the hole is damaged, it will increase to a certain extent. The field investigation results show that the gas extraction effect is enhanced by the collapse of double ?350 mm holes. For the double ?350 mm hole, the drainage radius is 2 m, the gas flow can be 21 times that of the ?100 mm hole, and the total volume of extraction is more than 10 times and even 40 times of the ?100 mm hole.