考虑颗粒破碎的井下垮落体挤压变形破坏规律研究

Coal breakage will occur during the formation of the rapid relief channel using the extension technique in the collapse body. Understanding the particle breakage law and the effects of breakage on the deformation and failure rules of the collapse body during the extension is the theoretical basis for the formation of the rapid relief channel. First, the fractal dimension computational model in the fragment scale is built based on fractal theory; secondly, large-scale triaxial tests are conducted according to the falling bodies with different fractal dimensions; with the relative breakage rate introduced to quantify the breakage extent. Then the breakage law is revealed by determining the relations between the fractal dimension and the relative breakage rate. Furthermore,，a cohesive zone model is employed, combined with the stochastic granular discontinuous deformation method to simulate the breakage of coarse aggregates, with the numerical model established. The effects of the loading rate, the microscopic parameters and the relative breakage rate on the movement laws, stress-strain relationships and the total energy dissipation during the loading process are analyzed using the numerical model with and without considering the particle breakage. Finally, the variations of the support stress with the stress between the particles, the stress against the support and the displacement under the different relative breakage ratios are addressed using the mechanical property model test of the collapse body during the rapid channel formation. This project has important theoretical significance to deeply understand the deformation and failure rules of collapse bodies including particle breakage effects from the macro- and micro- views, and provides theoretical basis for the support mechanism of the emergency rescue channel formation in underground collapse bodies.

在垮落体中以扩展方式形成快速救援通道时，势必造成垮落体再次破碎。掌握其挤压变形破坏规律，是快速建立安全救援通道的理论基础。首先，基于分形理论建立碎块尺度分布分形维数计算模型。其次，针对不同分维数的垮落体进行大三轴试验，引入相对破碎率衡量垮落体的破碎程度，确定分维数和相对破碎率的关系，揭示垮落体颗粒破碎规律。进而，在随机颗粒不连续变形方法基础上引入黏聚力模型和界面单元考虑垮落体颗粒破碎问题，构建垮落体的三轴试验细观模型，从细观尺度分析加载速率、细观参数和相对破碎率对垮落体的运动规律/应力-应变关系/加载过程总能量耗散的影响；最后，进行扩展形成巷道颗粒体的力学特性模型试验，研究相对破碎率、支护作用力与颗粒的作用力、颗粒间相互作用应力及其位移变化规律关系。研究成果有助于从宏细观两个尺度加深对考虑颗粒破碎的垮落体挤压变形破坏规律认识，并为巷道垮落体中再造应急救援通道支护机理研究提供理论基础。

以巷道垮落体为背景，研究了散体的力学特性，分析了散体的受力特征，探索了不同扩充方案下散体稳定性。通过相似级配法制备出实验的煤岩散体材料，对煤岩散体进行大三轴压缩破碎实验，分析并研究了散体的力学特性和分形特征。首先对单一粒径的煤岩散体进行压缩破碎实验，分析研究材质、粒径对散体的名义单轴抗压强度和破碎率的影响；制备出级配不同的煤岩散体，分别对其进行大三轴压缩破碎实验，计算出实验前后煤岩散体的分形维数、相对破碎率和改进相对破碎率；并分析了材质、级配对散体的分形维数、相对破碎率和改进相对破碎率的影响。在理论分析的过程中，以散体力学作为理论基础，对下方受力的垮落体进行了受力分析。在扩充形成通道时，上方的垮落体会形成4个相对应的滑移面，将垮落体分成位移逐渐变化的三个部分。在相似模拟实验中，以扩充通道的尺寸与垮落体的粒径作为基础变量。从影响范围来看，垮落体高度的增加使得影响范围扩大，对比不同通道尺寸，通道尺寸的增加使得影响范围增加。在横向数值模拟实验中，对比变量为煤岩属性、内摩擦角、通道尺寸以及垮落体粒径。通过所得到的位移云图，垮落体位移分为三个区域，稳定区、直接位移区、间接位移区。通道尺寸增加对垮落体位移影响较为稳定，呈现递增的状态。在纵向数值模拟实验中，对比的变量为煤岩属性、内摩擦角、通道尺寸以及垮落体粒径。证明了岩石颗粒的整体稳定性优于煤的稳定性。当通道尺寸为0.8m、1m、1.2m三种尺寸，上方斜坡相对比较稳定的区间，而在1.2m到1.5m之间，上方斜坡影响会突然的增加，因此在扩充时，保证通道的尺寸在1.2m以下。本研究可为应急救援通道的合理布置及快速救援提供指导。