复杂条件下平缓层状结构采动斜坡变形演化及稳定性判据研究

Deformation failure of gentle layered slope induced by coal mining, often occurs in slopes with a hard top layer and a soft bottom layer, and with upper steep slope and lower easy grade slope; the goaf locates at the lower easy grade area. The slope stability is influenced by the slope height, the location of goaf and the repeated mining, and the deformation evolution mechanism and stability evaluation criteria are unclear. The project adopts field investigation and geophysical prospecting combined with statistical analysis methods. 18 geological conceptual models under complex conditions are established. A statistical damage constitutive model is established to reflect the coupled stress state of overburden tension shear and the expression of the damage factor is presented for the parameters of mining and the damage of rock mass. The characteristics of damage factor evolution are analyzed by finite element method. By using the discrete element and centrifuge simulation test, the coupling law of overburden fracture and slope deformation and evolution is studied under the conditions of slope height, location of goaf and multi-layer mining. Based on the statistical analysis of the relationship between the damage factor and the deformation evolution of the slope, the deformation criterion of the mining slope based on the mining parameters - damage factor is established. Two mining collapse (landslides) will be selected for application. Finally, the evolution mechanism and the law of slope deformation under underground mining is revealed. The evaluation criterion of slope deformation stability is put forward. It provides a theoretical basis for correctly evaluating the stability of mining slopes.

地下采煤引起的平缓层状结构斜坡变形破坏，多发生在上硬下软、上陡下缓的斜坡中，采空区位于下部缓坡部位。采动斜坡稳定性受坡高、采空区位置和重复采动等影响显著，而变形演化机理和稳定性评价判据不清。项目采用工程地质测绘、物探结合统计分析方法，建立复杂条件下18种地质概念模型；建立反映覆岩拉张-压剪耦合应力状态的统计损伤本构模型，提出以采动参数和岩体损伤为变量的损伤因子表达式，采用有限元法分析损伤因子演化特征；采用离散元和离心机模拟试验方法，研究坡高、采空区位置、多层采动等条件下，采空区-斜坡系统内外变形耦合演化规律；统计分析损伤因子与采空区-斜坡变形演化的关系，建立以采动参数-损伤因子为依据的采动斜坡变形稳定性判据；选取两个采动崩塌/滑坡进行应用。揭示地下采矿作用下平缓层状结构斜坡变形演化机理和规律及其影响因素，提出采动斜坡变形稳定性评价判据，为正确评价采动斜坡稳定性提供理论基础。

地下采煤引起的平缓层状结构斜坡变形破坏，多发生在上硬下软、上陡下缓的斜坡中，采空区位于下部缓坡部位。采动斜坡稳定性受坡高、采空区位置和重复采动等影响显著，而变形演化机理和稳定性评价判据不清。本项目针对上述问题，以工程地质测绘、物探结合统计分析、数值模拟、离心机物理模拟、监测数据分析为手段，完成了复杂条件下平缓层状结构采动斜坡变形演化及稳定性判据研究工作，获得了以下6个方面的研究成果：①建立了贵州省采动斜坡工程地质概念模型，综合反映坡体结构、岩性、地貌、水文地质条件等工程地质条件与地下开采强度和开采位置等采空区参数共同作用的采矿滑坡工程地质分类模型；②揭示了采空区覆岩应力特征与岩体采动损伤特征，在缓倾内粉砂岩高陡斜坡中，当采空区外边界跨越坡脚时，采空区内边界岩体应力环境为高围压，外边界岩体应力环境为低围压，外侧采空区覆岩极易产生破坏；③揭示了缓倾内粉砂岩高陡采动斜坡覆岩损伤与变形机理，定义了采空区边界偏移距表述采空区与坡肩、坡脚的位置关系。坡肩、坡脚同时位于采空区上方时，变形破坏模式为塌陷倾倒。仅坡肩位于采空区上方时，变形破坏模式为塌陷滑移。采空区外边界远离坡脚和仅坡脚位于采空区上方时，变形破坏模式为塌陷推挤；④分析了岩体结构模型对采动滑坡成因机制的控制原理，建立了常见层状结构斜坡和斜坡条件下采矿滑坡的塌陷-拉裂-剪断、塌陷-拉裂-倾倒、塌陷-拉裂-滑移（剪断）、塌陷-拉裂-坐落、沉陷-溃屈等地质力学模式；⑤基于大型离心机模拟揭示山区采动斜坡变形机理，发现软弱层岩体的长期重力蠕变和后缘拉裂缝的扩展使斜坡内部岩体成为控制斜坡稳定性的关键块体；⑥基于采矿滑坡全过程模拟建立了采矿滑坡变形演化的时间-位移关系曲线，提出了采煤沉陷向滑坡启动转化的地质判据。