基于基岩风化带裂隙损伤演化与渗流规律的高承压厚松散层突水机理研究

Aquifer of strong water abundance in the bottom of cenozoic loose bed in the North China type coalfields,are directly occurrence at the top of the bedrock,it tends to have very high pressure if the cover thickness of loose bed is large.In recent years,water inrush disasters caused by coal mining under the loose aquifer of high water pressure,seriously threatens the coal mine safety production.Water inrush is often accompanied by abnormal enlargement of the roof pressure behavior,even crush the fully mechanized mining support,such disasters not only related to the hydrogeological conditions of high pressure loose bed ,but also the engineering geological conditions,the structure of overlying strata between the loose bed and coal seam,and it is closely related to the characteristics of rock fracture movement in the mining process.There is sufficient evidence to show that the primary fissure of bedrock weathering zone under loose bed and the hydrological and engineering geological characteristics play an important role in the pressure frame of water inrush under the loose aquifer of high water pressure.This article through analying the hydrogeology and engineering geological conditions of the loose bed,studying the movement of overlying strata and the failure law under the influence of mining conditions.And combining the water inrush hydrogeology and engineering geological conditions with the rule of the primary fissure of bedrock weathering zone under loose bed, damage evolution of the primary fissure under the mining conditions,fissure zone seepage characteristics and the movement of overlying strata and the failure law,using the simulation experiment,theoretical research and field test,will reveal the mining water inrush mechanism under the loose aquifer of high water pressure.

我国华北型煤田新生界松散层底部富水性较强的含水层，直接赋存在煤系基岩顶部，若松散层覆盖厚度较大，该含水层水往往具有很高的承压性。近年来，高水压松散含水层下采煤引起的突水灾害，严重威胁煤矿安全生产。突水时常伴随有顶板压力显现异常增大甚至将综采支架压死，此类灾害不仅与高承压松散层的水文地质条件有关，还与松散层与煤层之间的岩层的工程地质条件、覆岩结构有关，并与采动过程中岩层破断运动特征紧密相关。有充分证据表明松散层下基岩风化带原生裂隙的发育及水文工程地质特征对于高水压松散含水层压架突水有着重要的影响作用。课题拟通过松散层水文地质、工程地质条件分析、采动条件下影响覆岩运动和破坏规律研究。并将突水水文地质、工程地质条件与基岩风化带原生裂隙的发育规律、采动条件下原生裂隙的损伤演化、裂隙带渗流特征覆岩运动和破坏性规律相结合，采用模拟实验、理论研究和现场实测，将揭示高水压厚松散含水层下开采突水机理。

我国华北型煤矿煤系地层之上广泛赋存新生界松散含水层，煤层临近高承压厚松散含水层开采时，在水压与采动应力共同作用下容易引发顶板突水灾害。课题以高承压厚松散含水层水害典型矿井祁东煤矿为研究背景，采用理论分析、数值模拟、物理模型实验及现场实测等多种手段，分析了高承压厚松散含隔水层空间结构与水文工程地质特征，探查了煤系地层基岩风化带原生裂隙发育及高承压水作用下扩展演化规律，获得了采动覆岩变形破坏特征与裂隙损伤-渗流演化模型，揭示了高承压厚松散含水层突水机理。研究结果表明：（1）随着“四含”厚度增加，组成颗粒变粗，含粘量降低，富水性增强；突水事故主要集中在谷口冲洪积扇沉积区与厚松散层区。（2）基岩风化带泥质含量越大，裂隙密度越小；越靠近风化带顶界，裂隙密度与垂向裂隙比例越大。（3）基岩风化带岩石强度显著降低，粘结力和内摩擦角变小；渗透性弱-中等，实测阻水系数0.11~0.31MPa/m，不同部位隔水能力有一定变化。（4）高承压水对风化带原生裂隙扩张演化具有明显促进作用，模拟研究结果显示风化裂隙先后经历“扩容”与“扩展”两个阶段。（5）基岩风化带岩石渗透性与水压，原生裂隙发育密度和扩张演化程度有着明显的正相关性。（6）根据模拟和探测结果，“下渗带”发育深度平均10.24m，且与水压值大致成线性正比关系递增。采用弹塑性理论推导出考虑高承压水对岩体裂隙扩容与挤压劈裂破坏作用下的下渗带发育深度计算公式，与实测数值基本一致。（7）“四含”水位下降速度与矿压显现规律和位置相关，水位回升速度取决于水源补给速度和采动引起的水压力差。（8）“下渗带”的存在导致防水煤柱有效高度大大降低，当采动导水裂隙波及“下渗带”，高承压四含水涌入，从而引发导致压架突水灾害。（9）从突水特征与机理出发，提出支撑支架选型、煤壁加固、开采速度优化、下渗带注浆改造等防范技术措施。研究成果对高水压松散含水层下提限开采与突水灾害防治，具有重要的理论意义与实践价值。