深部煤矿软岩巷道围岩大变形破坏的多尺度损伤力学机制研究

In recent years, a lot of roadways in China coal mines have went into great depth. As the depth of the tunnel increase, the large deformation failure of surrounding rocks such as roof subsidence, floor heaving and sidewall shrinkage, become more severe and happens more frequently. The failure phenomenon caused by excavation activity in the rock masses under high in-situ stresses, is a process of stress redistribution and development of irreversible deformation coupled with damage evolution in multi-scale. At present, studies on damage mechanics of coal and sedimentary rock mass and large deformation mechanism of deep soft rock tunnels at great depth progressed slowly, has great effect on safety and efficient mining of coal resources in our country. In this project, we will investigate this problem by experimental, numerical and theoretical method. The experiment study includes the damage investigation for mechanical tests on coal samples, simulated fractured rock samples, and geotechnical physical model tests of deep coal mining in fractured rock masses. Based on microplane theory and two-phases assumption, an anisotropic damage constitutive model will be established for coal and sedimentary rock masses. A FE program of this model will be developed for numerical simulation of large deformation failure of tunnels in deep mining, to study the damage coupled deformation mechanism of the surrounding rock masses. The research results can be applied to stability analyses and support design of deep coal mine. Meanwhile, it will improve the study of the damage mechanics of the rock mass to a higher level.

近年来我国多数煤矿矿井已转入深部开采，巷道的冒顶、底臌、收帮等围岩大变形破坏现象频发，给巷道的维护带来极大的困难。深部高地应力和开采扰动引起的围岩大变形破坏是一个应力重分布、不可逆大变形发展与其内部不同尺度裂隙扩展的损伤耦合作用过程。目前，煤岩体损伤力学和软岩巷道工程大变形破坏机理研究进展缓慢，迄今为止仍是制约我国煤炭资源安全高效开采的瓶颈问题。本项目拟采用试验、数值模拟和理论研究相结合的手段，开展煤、裂隙岩体模拟试件的损伤力学试验研究和裂隙化软岩巷道工程的地质力学模型试验研究，在微平面和二元介质理论框架下建立煤岩体的微平面损伤本构模型，编制有限元计算程序用于软岩巷道工程的大变形力学分析，探求深部煤矿软岩巷道围岩大变形破坏的多尺度损伤力学机制。研究成果可为深部软岩工程的稳定性分析和支护设计提供指导，对岩体损伤力学的发展具有重要的理论意义。

近年来我国多数煤矿矿井已转入深部开采，巷道的冒顶、底臌、收帮等围岩大变形破坏现象频发，给巷道的维护带来极大的困难。本项目对深部节理化软岩巷道大变形破坏的多尺度损伤力学机制展开研究，主要研究内容包括：1）煤岩体三维裂隙网络重建技术和损伤力学机制研究；2）节理化软岩巷道工程大变形破坏的小尺度模型试验研究；3）煤岩体微平面损伤本构模型研究及有限元计算程序开发；4）节理化软岩巷道围岩大变形破坏的损伤力学机制数值模拟研究。.取得的重要成果：1）基于CT扫描试验，采用数字图像处理相关软件完成了煤岩体三维裂隙网络结构的重建，计算了裂隙组构张量、分析了三轴压缩下煤岩体的细观损伤力学机制；2）在含孔洞节理模型的单轴和双轴压缩试验中采用了应变仪、声发射、数字散斑等多种量测手段，研究了节理倾角和节理连通率对模型力学行为的影响规律。由于节理的存在，应力应变曲线可能变为多峰型（软化段多峰型、多峰平台后软化型）、声发射事件数显著增多、洞周监测点的应变和位移显著增大；上述力学响应具有明显的各向异性特征；3）煤岩体微平面损伤模型能较好地刻划准脆性材料宏观非线性力学行为（如应变软化、剪胀等），且可揭示其各向异性细观损伤力学机制（各方向微平面上岩石和裂隙面两个力学基元的非线性响应、裂隙面基元比例的变化即损伤演化）；4）对节理岩体单轴压缩的细观损伤力学机制开展了PFC模拟分析，发现节理系统的闭合和承载力的充分调用导致多峰型曲线和试件延性的增加。对含孔洞节理试件的单轴压缩开展了ABAQUS有限元模拟分析，研究了孔洞周围和节理周边岩桥的应力集中规律，较好地解释了模型的各向异性起裂机制和损伤演化行为。.本项目成果可为深部软岩工程的稳定性分析和支护设计提供指导，对岩体损伤力学的发展具有重要的理论意义。