西部黄土覆盖区采煤地面形变灾害机理研究

Geological hazards and environmental problems caused by mining have become a hot topic that focused and studied by countries in the world. Western loess covered area is the focus of regional development of coal resources of China in twenty-first Century. The surface subsidence deformation caused by Massive underground coal mining and its derivative disaster is more serious than other mining area, its particularity is related to the thickness of the soil, loess characteristics, groundwater, topography and other factors, it belongs to the.multi interdisciplinary subject, and the current academic research is still not sufficient. This project intends to divide the overlying bedrock and loess layer into two kinds of medium, based on mining subsidence and soil mechanics theory, reveals the mechanism of overlying bedrock and loess layer mutual feedback effect on mining subsidence, and the mechanisms of consolidation deformation of saturated loess, and volume change of unsaturated loess, loess collapsibility deformation and slope sliding deformation of "micro" deformation caused by bedrock surface dynamic subsidence. Based on this, to establish the prediction model of surface subsidence and deformation of loess mountainous areas, limit equilibrium theory model of loess slope mining, integrate SAR ground deformation measurements with inversion of gravity data. Create ground stability evaluation model, thus, create mining disaster evaluation system of loess coverage area, provide theoretical and technical support for the Western mining area disaster prevention and reduction and ecological protection.

煤矿区开采引起的地质灾害与环境问题已成为世界各国关注和研究的热点课题。西部黄土覆盖区是我国二十一世纪煤炭资源开发的重点区域，大规模地下采煤所导致的地表沉陷变形及其衍生灾害比其它矿区更严重，其特殊性与土层厚度、黄土特性、地下水、地形等因素相关，属于多学科交叉课题，目前学术界研究尚不充分。本项目拟将开采煤层上覆基岩和黄土层分为两类介质，基于土力学和开采沉陷理论，揭示采煤沉陷中的基岩与土层的互馈作用机理，以及基岩面动态沉陷引起的饱和黄土固结变形、非饱和黄土体积变形、黄土湿陷变形、山坡滑移变形等“微观”形变机理。在此基础上，建立黄土山区地表沉陷与变形预测模型、采动黄土斜坡极限平衡理论模型、融合地面SAR变形测量和重力测量数据反演、建立采空区地面稳定性评价模型，从而构建黄土覆盖区采煤地面形变灾害评价体系，为西部矿区防灾减灾与生态保护提供理论与技术支持。

本项目研究了西部黄土覆盖区采煤地面形变损害的特殊性及其与地貌条件、土层特性、基岩特性、开采参数之间的关系，揭示了黄土矿区开采沉陷过程中出现的多种附加变形与地表损害及其形成机理。主要附加变形可归结为：因地表土层沉陷弯曲引起的水平向附加应力为主所造成的近地表非饱和土体单元体积变形；因开采沉陷引起地下水位降低导致土体有效应力增大所造成饱和黄土失水产生固结变形；因地表土体剪切破坏和裂缝导致地表水渗入湿陷性黄土层所造成的土层湿陷变形；黄土沟壑区采动斜坡因应力场变化所产生的指向下坡方向的塑性滑移变形。开采沉陷过程中因水平向附加应力导致土体剪切形成地表裂缝，引发黄土层整体结构破坏，近地表土体单元因体积变形导致土体密实度、含水量、力学特性发生改变，从而造成地面形变损害甚至诱发山体滑坡。通过实验分析了土体单元体积变形与土体内聚力、内摩擦角等力学参数的关系，建立了“开采沉陷变形”与“斜坡稳定性”之间的联系。在此基础上，将黄土矿区地表沉陷分解为黄土层荷载效应下的基岩开采沉陷以及基岩面不均匀沉降导致的黄土层沉陷变形，建立了黄土覆盖区土层与岩层双层介质的开采沉陷模型，通过数值模拟确定了黄土层自重对于基岩沉陷的荷载效应及这种荷载效应与开采充分程度之间的量化关系，导出了适合黄土矿区的双层介质概率积分法预计模型，基于实验和土力学原理构建了采动黄土层各种附加变形的预计模型。根据重力场理论导出了长壁工作面采空区地表重力异常的计算模型，提出了基于地面重力异常数据反演采空区边界及深度变化的原理方法。在矿区形变损害现场监测试验中，利用 InSAR、无人机LiDAR等多源遥感技术提取地表沉陷损害全盆地精细特征，基于开采沉陷的对称原理构建了矿区InSAR LOS向位移的三维分解模型并进行了算法实现，提出了激光点云构建采煤沉陷模型和无人机影像提取采动裂缝的改进方法，为西部复杂地理环境下矿区地表形变损害研究提供了有效的技术支撑。