运用奥陶系顶部灰岩隔水层安全穿越地堑研究

Research on Limestone Aquifuge in Top Ordovician and Its Application in Roadway Excavated Through Graben Faults

针对华北煤层与底板的奥陶系岩溶承压含水层之间隔水层太薄而威胁煤矿开采问题,提出了奥陶系顶部存在碳酸岩隔水层的观点.以潞安矿区王庄煤矿暗斜井穿越地堑等大型断层组为实验现场,运用岩石成分分析、微孔隙结构测试、井上下地质及水文地质钻探、试验等宏、微观等手段,对该井田奥陶系顶部岩层渗流特性及断层组演化历史进行研究,结果表明:1)分别在该矿井田内的峰峰组顶界面下60,130 m存在含水段,即奥陶系顶部存在厚度大于60 m的碳酸盐岩隔水层;2)该段隔水岩层的岩性为粗粉晶～细砂晶石灰岩和生物屑灰岩,方解石占95%～100%,处于加里东期古风化剥蚀面附近而岩溶却不发育;3)各孔隙结构参数与上覆本溪组伊利石泥岩相似,孔隙度(1.16%)甚至略低上覆泥岩,其隔水性能优于泥岩.4)奥陶系顶部碳酸岩隔水层加大了底板隔水层的总厚度和强度,断层组的采动活化段沟通岩溶含水层的几率减少,增强了防水安全系数,这已为暗斜井巷道的安全施工和成功穿越所证实.

We propose a viewpoint of carbonate aquifuge existing in the top of Ordovician to solve the problem that safety mining is threatened due to the thin water-resisting strata between coal seam floor and the upmost surface of Ordovician. In order to explore this problem, we took subinclined shaft through huge fault set in Wangzhuang coal mine of Lu＇an mining area as our experiment field, and studied seepage characteristic as well as evolution history of fault set for rock strata in the top of Ordovician in this coal mine by synthetically using macroscopic and microscopic methods including rock component analysis, micro-pore structure measurement, drilling exploration, and field measurement. The results indicate that 1） water-bearing section exists between 60 m and 130 m under the upmost surface of Fengfeng formation, which means that there is a carbonate aquifuge of more than 60 m in the top of Ordovician in this coal mine; 2） this aquifuge is mainly composed of fine-grain crystalized limestone, in which calcite accounts for 95%-100% and karst does not develop for locating near old weathering erosion surface of Caledon period; 3） every pore structure parameters are similar to overlying illite mudstone of Benxi formation, with better water-resisting capacity and even lower porosity （1.16%） than the overlying mudstone; and 4） the water-resisting section in the top of Ordovician enlarges the whole thickness and strength of aquifuge in coal seam floor, resulting in decreasing water-inrush risk for activity of fault set, which has been proved by the fact that subinclined shaft was excavated safely and successfully through graben fault set.