煤矿井下水砂突涌钻孔封孔技术研发与应用

Development and application of borehole sealing technology for water-sand inrush from Ordovician limestone aquifer in coal mine

桑树坪煤矿采取地面注骨料和井下注浆技术治理奥灰(奥陶纪灰岩)岩溶陷落柱时,施工的3个常规检查钻孔出现严重的水砂突涌现象,封孔难度极大,采取向孔内下入木楔、反丝止浆塞等方法均封孔失败。针对此难题,提出带压顶替注浆封孔技术,首先,向孔内注入大于套管体积的清水以确保孔内通畅,避免砂粒填充至套管内,导致封孔深度未达到套管以下稳定岩层;之后,采取低泵量向孔内多次循环注入大于套管体积的稀水泥浆;最后,待水泥浆凝固后,采取小直径钻头钻进至套管外以检查大孔径钻孔的封孔质量。该技术成功应用于3个常规检查钻孔封堵工程,实践发现:先期注浆封孔水泥浆液水灰比宜选取1︰1,单次候凝时间宜选取3~4 d,延长水泥浆候凝时间,可提高钻孔封孔质量。此技术适用于井下狭小空间作业,可防止孔口涌水涌砂,避免孔内水砂高速流动,确保封孔质量及人员安全,为封堵类似水砂突涌钻孔提供技术借鉴。

The technology for surface sand filling and underground grouting is adopted to control the karst collapse column of Ordovician limestone in Sangshuping Coal Mine.However,there are serious water-sand inrushes in three conventional inspection boreholes,so it is of great difficulty to seal them.Putting wooden wedges and reverse wire packers into the boreholes all fail.In order to solve this problem,the grouting sealing technology with pressure replacement is proposed in this paper.Firstly,water larger than the casing pipe volume is injected into the borehole to ensure a clear borehole and to avoid sand filling into the casing pipe,resulting in the sealing depth not reaching the stable rock layer below the casing.After that,a lower pumping volume is adopted to repeatedly inject cement slurry larger than the casing volume into the borehole.Finally,after the cement slurry is solidified,a small diameter bit is used to drill outside the casing to check the sealing quality of the large diameter boreholes.Three conventional inspection boreholes are successfully sealed.In the engineering practice,it is found that the water-cement ratio of the cement slurry for early grouting borehole sealing should be 1︰1,and the single setting time should be 3 to 4 days.Prolonging the cement setting time can improve the quality of borehole sealing.This borehole sealing technology is applicable to underground narrow space operation,which can prevent water-sand inrushes from the orifice,ensure the sealing quality and personnel safety,and provide a technical reference for sealing similar water-sand inrushes.