厚松散层薄基岩下采动裂隙发育规律及应用

Developing Rule and Engineering Application of Mining Fracture under Thick Unconsolidated Layers and Thin Bedrock

为研究厚松散含水层薄基岩下厚煤层综放开采的安全性,从黏土采动隔水性和近第四系底部导水裂缝带发育特征两个方面进行了讨论。以潞安矿区三元煤矿为例,通过对开采区域第四系松散层的不同深度进行取样和实验室试验分析,得到了特定地质条件下黏土的物理力学特性和水理特性。通过选取合理的黏土隔水层采动失稳判据,评价分析了第四系底部厚黏土隔水层综放高强度开采后隔水性能的变化状态。采用数值模拟和现场实测方法研究了厚松散层薄基岩条件下近第四系底部覆岩破坏和采动裂缝发育规律。研究表明:①三采区第四系松散层黏土随着埋深增大,其力学性能呈增大趋势,埋深超过130 m时,黏土的液性指数甚至降至0以下,深埋黏土具有良好的原生隔水性能;②黏土采动隔水性评价结果表明,区内第四系底部黏土采动后仍然具有良好的隔水能力,能很好地抑制导水裂缝带上行扩展;③近第四系底部开采导水裂缝带高度仅发育至第四系底部黏土。实例分析表明:三元煤矿3301工作面在顶板基岩厚度仅为36~55 m、煤层厚度7 m的情况下,实现了地表水体和第四系松散含水层水体下的综放安全开采,为类似水体下采煤实践提供了有益参考。

In order to study the mining safety of high seam with fully mechanized top-coal caving technology under thick unconsolidated aquifers and thin bedrock,the study work is carried out from two aspects:the water-resisting property of clay in mining and the development characteristics of the water flowing fracture zone at the bottom of the Quaternary.Taking Sanyuan Coal Mine in Lu’an mining area as the study example,through sampling and laboratory test analysis of different depths of Quaternary loose strata in mining area,the physical and mechanical properties and water properties of clay under specific geological conditions are obtained.The change of water-resisting performance of thick clay aquifer at the bottom of Quaternary system after fully mechanized top-coal caving mining with high strength is analyzed by selecting reasonable criterion for mining instability of clay aquifer.The law of overburden failure and mining fracture development at the bottom of Quaternary under the condition of thick loose bedrock and thin bedrock is studied by numerical simulation and field measurement.The study results show that:①the mechanical properties of Quaternary loose clay in No.3 mining area of the mine increase with the burial depth increasing,when the buried depth exceeds 130 m,the liquid index of clay even decreases to below 0,the deep buried clay has good primary water-proof performance;②the evaluation on water-resisting property of clay in mining show that the clay at the bottom of Quaternary system in this area still has good water-resisting property after mining,and can well inhibit the upward expansion of water-conducting fracture zone;③the results of numerical simulation and field measurements indicate that the height of aquifer fractured zone exploited at the bottom of Quaternary only develops to the clay at the bottom of Quaternary.The application results show that fully-mechanized caving mining under surface water and Quaternary unconsolidated aquifer water is successfully realized in 3301 working face of Sanyuan Coal Mine with the thickness of roof bedrock only 36~55 m and the thickness of coal seam 7 m,which provides engineering reference for coal mining practice under similar water body.