渗流影响下矸石充填体蠕变性能及细观力学特性研究

In the process of the comprehensive mechanized solid filling mining, the creep behavior of filling body under seepage condition is the basic research subject of overburden control and surface collapse prediction in filling area On the basis of laboratory test, combined with theoretical analysis and numerical calculation, the creep constitutive relationship of gangue filling body under the influence of water seepage will be studied in this project. And the effects of soil-rock ratio, particle size (Talbol power exponent), initial porosity and water pressure on creep parameters are investigated. Based on the experimental results of lateral compression, triaxial compression and seepage creep, a theoretical model of fluid-solid coupled compaction creep is established and its mechanical properties are analyzed. The discrete element numerical models are established by using discrete element method, the CFD-DEM coupling operation and image processing techniques. Considering the actual shape of particles, particle breakage and fluid-solid coupling, the micromechanical characteristics such as particle breakage, velocity distribution, liquid bridge force and force chain shape are analyzed, which establishing a relationship with the macroscopic mechanical characteristics such as gradation, strength, strain, permeability, etc. The purpose of the study is to explore the influencing factors of fluid-solid coupling compaction creep of bulk materials and the corresponding meso-mechanics mechanism of bulk materials, to provide basic theoretical support for filling mining technology. And at the same time, the research results of this project can be used for reference for the control of rock strata in the filling area under the condition of groundwater seepage.

渗流条件下充填体的蠕变性能是综合机械化固体充填开采覆岩控制、地表塌陷预测的基础性研究课题。本项目以室内试验为基础，结合理论分析和数值计算等手段，研究水渗流影响下矸石和土混合充填体的蠕变本构关系，探索土石比、粒径（Talbol幂指数）、初始孔隙度、水压等对蠕变参量的影响规律。根据侧限压缩、三轴压缩和渗流蠕变试验结果，建立流固耦合压实蠕变理论模型，分析其力学性质。利用离散单元法、CFD-DEM耦合运算和图像处理等技术建立相应的离散元数值模型，在考虑颗粒实际形状、颗粒破碎及流固耦合的条件下，分析颗粒破碎、速度分布、液桥力、力链形态等细观力学特征，与充填散体物料的级配、强度、应变、渗透率等宏观力学特征之间建立联系，探寻散体物料的流固耦合压实蠕变的重要影响因素和相应的细观力学机理，为充填开采技术提供基础理论参考，同时为有地下水渗流条件下充填区的岩层控制提供借鉴。

渗流条件下充填体的蠕变性能是综合机械化固体充填开采覆岩控制、地表塌陷预测的基础性研究课题。本项目综合运用多种手段，对矸石充填体的蠕变渗流宏细观力学性质展开研究，得到以下结论：. （1）侧限压缩试验显示矸石充填体的应力-应变满足对数关系，适当增大细小颗粒、石灰或水含量，都有利于提高抗压缩性能。用离散元簇单元模拟侧限压缩和双轴压缩，发现含石率大于50%以后，强力链的贯通性逐渐下降，力链也发生倾斜。引入振动机制，增大频率或振幅均能提高夯实机构对充填体的夯实效果。建立了充填综采支架-顶板-充填体力学模型，计算发现初始充填高度是控制顶板岩梁下沉的决定性因素，相似模拟试验规律与理论计算结果吻合。. （2）压缩蠕变试验显示矸石充填体应变-时间关系符合Kelvin-Volgt模型、孔隙率-时间关系符合衰减指数模型。试样粒径越小或应力水平越高，越容易发生蠕变破碎，破碎造成的位移突变的比例随应力水平的增加而降低。随着颗粒重排与破碎，岩石颗粒级配更加合理，最终抑制了颗粒的重排。颗粒流模拟显示应力集中于颗粒接触点处，裂隙的扩展使力链路径及位置发生改变，力链分布更加均匀。接触的断裂贯穿于整个蠕变过程，表明虽然试样整体蠕变位移趋于稳定，但试样内部部分岩块发生蠕变损伤，处于蠕变加速阶段。. （3）设计了矸石充填体蠕变渗流试验装置和“破碎岩体非线性渗透力学分析系统V1.0”，试验显示渗流梯度与流速呈非线性关系，渗透率与轴压负相关，非Darcy因子与轴压正相关。由于细小颗粒的运移会改变内部渗流通道的连通性，所以渗透特性稳定的时间晚于蠕变开始稳定的时间。通过多场耦合软件COMSOL Multiphysics建立模型，施加渗透压，发现渗透特性经历了急剧变化和缓慢变化两个阶段，与渗流试验结果基本相符。结合蠕变本构关系和流固耦合动力学理论，建立蠕变渗流耦合力学模型，得到了矸石充填体在蠕变稳定状态时的渗流系统平衡态方程。项目研究结果可以为充填开采技术和有地下水渗流条件下充填区的岩层控制提供基础理论参考。