采动应力路径下煤体中裂隙演化规律及破坏失稳机理研究

The pre-existing flaws in coal mass predominate their strain, failure and the mechanical properties. The interaction between pre-existing flaws (PEFs) and mining induced stress paths (MISPs) are key points that affect coal mass behaviors. This project takes coal mass containing pre-existing flaws as the research object. And the two key elements: “pre-existing flaws” and “mining induced stress paths” are taken into account. Firstly, the PEFs in microscopic scale will be reconstructed by CT scanning and images segmenting technologies, and determining the characters of the flaws. Then mining-induced mechanics experiments on larger scale (Φ10×20 cm) coal mass will be carried out under the MISPs. The initiation, propagation and extension rules of the mining induced fractures will be studied, and their communication with PEFs will be also presented. The effects law of PEFs and MISPs on mining induced fractures will be summarized. On this basis, the changes rules of macroscopic parameters (strain-stress relation, strain energy, damage, elasticity modulus, wave velocity and etc.) and microscopic parameters (mining induced fracture density and extension and distribution, fracture morphology of the rock bridge and its induced acoustic emission, etc.) at the failure and instability stages of the coal mass will be analyzed. The relation between changes rules of the macroscopic and microscopic parameters at coal mass failure and instability stages and PEFs and MISPs will be discussed. And then, the mining induced failure and instability mechanism of coal mass containing pre-existing flaws will be explained. Research results from this project will provide useful reference for accurate prevention and control of underground pressure in coal mining.

煤体中的原生裂隙控制着煤体的变形、破坏及力学性质，原生裂隙与采动应力路径之间的相互作用是影响围岩矿山压力显现的关键。本项目以含原生裂隙煤为研究对象，围绕“原生裂隙”和“采动应力路径”两个关键因素，首先通过CT扫描和图像处理技术三维重构煤体的细观原生裂隙，确定原生裂隙分布特征；而后开展采动应力路径下Φ10×20cm大尺寸煤体的采动力学实验，研究煤体内采动裂隙的发育、传播和扩展演化规律、与原生裂隙的连通形态，探究煤体原生裂隙、采动应力路径对采动裂隙演化规律的影响。在此基础上，分析煤体破坏失稳阶段宏观参数（应力应变关系、变形能、损伤参量、弹性模量、波速等）和细观参数（采动裂隙密度和扩展分布、岩桥破断形态及其诱发的声发射信息等）的变化规律；探讨煤体破坏失稳宏细观参数变化特征与原生裂隙和应力路径之间的内在联系，进而揭示含原生裂隙煤体的采动破坏失稳机理。研究成果可为矿山压力精确防控提供有益参考。

煤体中的原生裂隙控制着煤体的变形、破坏及力学性质，原生裂隙与采动应力路径之间的相互作用是影响围岩矿山压力显现的关键。本项目CT扫描重构了煤岩体受载前后的裂隙分布特征，分析了原生裂隙和受载形式对煤岩体裂隙发展的影响。提出了一种基于应力路径的煤岩体受载响应实验方法，分别实验研究了开挖应力路径下硬岩变形损伤的宏细观响应特征和不同损伤煤岩体采动应力路径下的渗透特性演化规律，分别获取了与现场观测比较一致的破裂机理和声发射震源机制和渗透系数演化规律，表明基于应力路径的实验方法可以更好的反映现场实际。基于离散元模拟方法，提出了一种考虑微观特性的受载岩体波速变化模拟方法，基于两个实例建立了岩石微观结构与波速的对应关系，分析了内部微观裂隙分布情况与波速变化的联系。采用大尺度相似模拟方法分析了原生硬层夹矸对顶煤破碎和冒放性的影响；采用工程尺度数值模拟方法分析了层理结构对顶板破裂冒落特征的影响、支护结构对顶板控制的影响。研究成果可为在室内精确的模拟工程实际提供有益参考。