浅埋特厚硬煤层过沟谷开采超前区域弱化控制技术

Weakening control technology in advanced region during mining through gully area in shallow buried extra-thick and hard coal seam

针对沟谷区域浅埋特厚硬煤层工作面回采过程截割困难、回采进尺低下、采煤设备损耗严重等问题,采用数值模拟和工程应用等综合方法,研发了煤矿井下本煤层定向长钻孔分段压裂弱化技术,探讨了分段水力压裂厚硬煤层弱化作用及裂缝形成机理,并在典型工作面开展了应用。结果表明:工作面回采方向与沟底走向夹角大于75°时,工作面超前支撑压力低,是造成厚硬煤层难截割的关键原因。通过分段水力压裂施工,可在煤层中形成走向、径向交互裂缝,与天然裂缝沟通形成裂缝体系,弱化煤体强度。孔内瞬变电磁探测显示,单个钻孔形成6个低阻异常区,压裂弱化影响范围最大为35 m。压裂后煤壁形态由直立完整变为明显破碎状,回采进尺由单日平均8.00 m提升至12.13 m,增幅51.6%,验证了特厚硬煤层弱化的有效性。

Aiming at the problems such as difficult cutting,low efficiency footage and serious loss of coal mining equipment during coal mining in gully area in shallow buried extra-thick and hard coal seam,the staged fracturing weakening technology with directional long borehole along coal seam in underground coal mine was researched and developed by comprehensive method of numerical simulation and engineering application,the weakening effect and fracture formation mechanism of staged hydraulic fracturing in thick and hard coal seam were discussed,and engineering application of the technology was carried out in a typical working face.The results showed that when the included angle between the advance direction of the working face and the bottom strike of the gully was over 75°,the advanced abutment pressure was low,which was the key reason for difficult cutting in thick and hard coal seam.Through staged hydraulic fracturing construction,strike and radial interactive fractures formed in the coal seam,which communicated with natural fractures and formed a fracture system,it could weaken the coal strength.The in-hole transient electromagnetic detection results showed that there were 6 low-resistivity abnormal areas formed in a single borehole,and the maximum impact range of fracturing weakening was 35 m.The shape of coal wall changed from upright integrity to obviously broken after fracturing,and the average daily footage increased from 8.00 m to 12.13 m,increased by 51.6%,which verified the effectiveness of weakening technology in the extra-thick and hard coal seam.