软岩保护层开采卸压增透效应及瓦斯抽采技术研究

Study on relief-pressure antireflective effect and gas extraction technology for mining soft rock protective seam

软岩保护层具有层位选择灵活性和开采厚度可调节性等特点,在首采卸压层或保护层选择上具有广泛的应用前景。以芦岭矿Ⅲ1采区为工程背景,通过不同保护层开采方案对比,选择软岩层作为首采卸压层,运用数值试验方法讨论软岩保护层开采卸压增透机理,在分析覆岩移动破坏特征的基础上,提出卸压瓦斯综合治理方案。研究表明:软岩保护层开采后,上覆被保护层(8~#煤)采空区范围卸压率和膨胀变形率分别为0.57和0.782%,被保护层出现卸压增透效应。8~#,9~#煤处于弯曲下沉带的下部范围,10~#煤处于底鼓变形带的上部范围,设计以地面采动井、拦截钻孔、穿层钻孔配合采空区埋管抽采为核心的卸压瓦斯抽采体系。考察期范围卸压瓦斯总抽采流量平均稳定在30.5 m3/min,8~#,9~#煤瓦斯预抽率达65.4%,有效地实现了煤、瓦斯与稀有矿产资源共采。

The soft rock protective seam has extensive application prospects in selecting the first relief-pressure layer or protective seam due to its flexible position and accommodative mining thickness. Using the engineering background of Ⅲ1 mining area in Luling coal mine, the soft rock seam is selected as the first relief-pressure layer by comparing mining schemes of different protective seams. Under the condition of coal seams group, the relief-pressure antireflective mechanism of soft rock protective seam mined is discussed using the numerical test methods. Based on analyzing overburden rock movement characteristics, the comprehensive treatment project of relief-pressure gas extraction is proposed. It is found that after mining the soft rock protective seam, the relief-pressure rate and the expansion deformation rate are 0.57 and 0.782%, respectively in gob of the overlying protected seam（8~#coal seam）. Meanwhile, there is relief-pressure antireflective effecting in the protected seam. 8~# and 9~# coal seams locate in the bottom of bending subsidence belt, while 10~# coal is at the top of the deformation zone in the floor heave. The different relief-pressure gas extraction system is designed at the core of surface drill well, intercept borehole, crossing hole and buried pipe in the gob. Within the scope of the investigation, the total extraction flow of relief-pressure gas remains stable at an average of 30.5 m3/min and the gas pre-extraction ratio reaches 65.4%, which effectively realizes the coproduction of coal, gas and rare mineral resources.