复杂地质条件下覆岩结构采动破坏特征及透水灾害预测研究

The water-inrush hazard of mine is closely related to the mining effect characteristics of the structure of overlying strata and the activation of fault. The different mining mechanical effect and water permeable performance of structure of overlying strata have different effects on water inrush. Based on the analysis of different lithology combination, coal seam occurrence characteristics, geological structure, mining stress distribution, the different structure model of overburden is established. The role of control of structure of overlying strata and the combination of geological structure on the mining effect of overlying strata and fault activation is studied by theoretical analysis, the similar material model test, numerical simulation method. The change of coefficient of permeability of different rock layers in mining process is obtained by Indoor servo permeability experiment. The corresponding relationship of rock permeability and lithology, the relationship of stress strain, rock structure is obtained. The three-dimensional fluid-structure coupled numerical model is established by similar material model test and FLAC3D and RFPA program. The displacement field, stress field, the distribution of pore water pressure and water seepage in mining is obtained. The permeability intensity index of structure of rock is suggested. The evaluation method of water permeability and disaster prediction is proposed by using subjective AHP method and the objective entropy method. The reliable technical support is provided for safety mining under water body.

矿井透水灾害与覆岩结构采动破坏特征及地质构造的活化紧密相关，不同的覆岩结构的采动力学效应和透水性能的差异对矿井突水产生不同影响。本研究在分析煤层不同岩性层组合、赋存特征、地质构造、采动应力分布等基础上建立不同的覆岩结构模型，通过理论分析、相似材料模型试验、数值模拟手段研究覆岩结构和地质构造组合对覆岩采动效应及断层活化的控制作用；运用室内伺服渗透实验及现场水力压裂试验获得采动过程中不同岩层渗透系数的变化规律，获得岩层的渗透性与岩性、应力-应变关系、岩石结构的对应关系；通过固液耦合的材料模型试验和基于FLAC3D和RFPA程序的二次开发，建立三维流固耦合数值计算模型，模拟煤层开采过程中覆岩结构的位移场、应力场、孔隙水压力分布以及在动态开采中水体渗流规律，提出覆岩结构透水强度指标，采用主观的层次分析法和客观的熵权法相结合建立矿井透水能力和灾害预测的评价方法，为水体下煤层安全生产提供可靠技术支撑。

矿井透水灾害覆岩结构采动破坏特征及地质构造的活化紧密相关，不同覆岩结构的采动力学效应和透水性能差异对矿井突水产生不同影响。为解决矿井透水所产生的相关灾害事故预测，本课题建立了覆岩的坚硬-坚硬型结构、软弱-坚硬型结构、坚硬-软弱型结构、硬软交替型结构及其与构造的组合模型，得出不同岩性组合导水裂隙带范围，其中软弱覆岩具有较强的塑变能力，导水裂隙带高度达约为150m。断层带附近综放开采导水裂隙带最大高度比无断层时增加约40％。断层存在形式及活化对裂隙导水性能具有主要影响作用，断层角度较低时，对导水裂隙带发展高度有限制作用，且随着断层倾角的增大而增大，当断层角度大于60°时影响甚微。获得了覆岩在加、卸载全应力-应变过程中渗透性与应力之间规律及采动覆岩渗透性变化及岩体结构破裂、裂隙扩展和导水通道的形成机制及其水力联系。随工作面推进，首先在切眼和煤壁支撑端发生拉伸和塑性变化，产生裂缝并扩展，渗透性提高，孔隙水压力增大；随工作面推进，顶板破坏高度增加，逐渐波及到上覆含水层，含水层水位下降，形成了以采空区为中心的降落漏斗。采空区中部覆岩破坏发育较低，随工作面推进，后方采空区逐渐呈压实状态，裂隙闭合，渗透性减小，水力梯度增加，孔隙压力减小。采用熵权-层次分析法通过Matlab编程获得导水裂隙带高度预测值及各影响因素权重。得出工作面倾斜长度和采厚是影响导水裂隙带高度的主要因素，进行了覆岩透水危险性影响因素分析；采用改进层次分析法，建立了复杂地质条件下覆岩透水危险性评价模型。对大平煤矿三台子水库下S2S9工作面综放开采进行了安全评价，得到水库范围内S2S9工作面开采安全性评价系数为0.715，确定留设防水煤柱条件下进行开采是安全的。本研究初步形成了复杂地质条件下厚煤层综放开采覆岩破坏、渗透规律研究成果及安全评价方法，为复杂地质条件下厚煤层矿井开采布局、开采顺序合理布置提供了理论保障，为煤矿透水灾害的预防预测提供了理论依据，实际意义较大。