大面积采动地层长期稳定性研究

Because of coal mining, the large, multi-layered, complex form of goaf and a large area of mining stratum is formed, the rock structure is weaken seriously, occurs the creep deformation continuously and is the long-term unstable. The project uses Fuxin mines as an example and intends to adopt a combination methods of theoretical analysis, experimental research,numerical calculation and field test, analyzing the relation between mining depth,mining thickness,dip angle,the goaf area and the formation of "three zones",the rock structure.It uses the folded reduction rate of the stiffness coefficient to describe the deformation characteristic of the creep fracture process of the rock. It uses the self-made experiment equipment to measure the creep fracture process of the rock sample and the changing law of the folded reduction rate of the stiffness coefficient with the time and the effect of the moistrue rate,disturbance intensity on the creep deformation,the folded reduction rate of the stiffness coefficient. Given the criterion of the rock tension creep fracture, the model of tension creep fracture is established. It establishes the model of disturbance-creep fracture-the folded reduction rate of the stiffness coefficient and moisture content-creep fracture-the folded reduction rate of the steffness coefficient of the large area of mining stratum,solves the analytical and numerical solution,develops the finite element program introducing the dynamic fracture element.Used in Fuxin mining, it simulates numerically the creep fracture evolution and the change of the folded reduction rate of the stiffness coefficient of the stratum of Fuxin mining,analyzes and gives the forming reason and conditions of the ground collapses and fissures of the large area mining stratum,puts forward the prevention measurement and treatment scheme.

煤矿地下开采形成面积大、多层位、形式复杂的采空区，地层结构严重弱化，持续发生蠕变变形，长期不稳定。项目采用现场考察、实验研究、理论分析、数值计算和现场应用相结合的方法，以阜新矿区为基础，分析采深、采厚、倾角、采空区面积等与"三带"形成及地层结构的关系。引入刚度系数折减率描述岩石蠕变破裂过程中的变形性质，采用自制实验设备测定岩样拉张蠕变破裂过程及刚度系数折减率随时间的变化规律，实测含水率、扰动强度对蠕变变形及刚度系数折减率的影响。给出岩石拉张蠕变破裂判据，建立拉张蠕变破裂模型。建立大面积采动地层扰动-蠕变破裂-刚度系数折减率及含水率-蠕变破裂-刚度系数折减率数学模型，求解解析及数值解，引入动态破裂单元开发有限元计算程序。在阜新矿区进行现场应用，数值模拟阜新矿区地层蠕变破裂演化及刚度系数折减率变化情况，分析给出大面积采动地层地面塌陷、地裂缝形成原因及条件,提出防治措施及治理方案。

煤矿地下开采形成面积大、多层位、形式复杂的采空区，地层结构严重弱化，持续发生蠕变变形，长期不稳定。项目以阜新矿区地层结构特征为基础，采用离散单元法模拟了不同工作面距离和采高下大面积采动地层结构演化过程；通过能量法分析顶板垮落过程，破裂之前外力做功全部转化为弹性势能储存，当弹性势能超过了岩梁的储能极限后，岩梁发生破坏。破坏时弹性势能转化为辐射能、热能和动能，将基本顶岩梁垮落过程释放的能量采用岩梁克服本身的抗拉强度发生破裂来进行计算，并给出了垮落过程中释放能量的计算公式；通过高速摄像机拍摄准静态加载下泥岩试件巴西劈裂过程，分为三个阶段：泥岩试件变形累计阶段（宏观无裂纹）、宏观裂纹稳定扩展阶段、宏观裂纹动态张裂阶段。在裂纹扩展过程中，表面第一主应变场变化明显，在开裂部位第一主应变最大；自制实验设备进行岩石拉张蠕变实验，分级加载下岩石的拉张蠕变也包括三个阶段：初始蠕变阶段、等速蠕变阶段和加速蠕变阶段；进行冲击扰动下圆盘试件拉张蠕变实验，扰动作用瞬时使得蠕变变形瞬时增大，并伴有一定程度的回落，表明扰动下所产生的变形不仅有弹性变形还有不可逆的塑性变形也就是微观的破裂；给出刚度系数折减率的概念并分析了软岩蠕变过程中刚度系数折减率的变化；对于大面积采动地层结构，煤层开采后在其顶部和地表处产生拉应力，形成拉应力区域，随着采空区范围的扩大，拉应力区域逐渐增大，对地表的影响也逐渐增大，拉应力区域的形状为近似漏斗形。最大拉应力出现在采空区的顶部，随着开采范围的增大地表处的拉应力随之增大，地表也越容易出现裂缝，破裂情况也更为严重；对于不同顶板岩层抗拉强度下的拉张破裂进行了模拟，抗拉强度越小，拉张破裂的区域越大，对地表的影响范围也越。项目所取得的研究结果不仅对采动地层的破裂、演化规律具有重要的理论意义，而且对采动地层灾害防治提供理论依据和技术指导。