单侧卸荷诱发深部金属矿采空区围岩损伤及强度劣化机理研究

The instability of mined out area in deep metal mines is essentially the overall failure caused by the strength degradation of surrounding rock under unloading stress. The macroscopic performance is the weakening of the mechanical parameters, and the microscopic appearance is the expansion of the fracture. At present, the inner connection between the meso damage of rock mass and the weakening of the macroscopic mechanical parameters was not clear, so the mechanism of the deterioration of the strength of the surrounding rock was not clear. Taking the surrounding rock of the gob in the deep metal mine as the research object, the study will focus on the fine damage identification and quantitative characterization of the fractured rock mass and the macroscopic mechanism of the deterioration of the deep fractured rock mass under the effect of single side unloading. Firstly, the true three axis mechanical experiments will be carried out for the rock mass containing a single group of fissures, and the change law of the macroscopic mechanical parameters of the fractured rock mass will be studied. At the same time, the evolution and spatial distribution of meso-damage will be revealed using the magnetic resonance and scanning electron microscopy, and the quantitative expression of damage variables based on the characteristic parameters of NMR will be established. Combining with image processing technology, 3D reconstruction will be carried out to realize the localization and recognition of meso-damage. Then, combined with the mesoscopic numerical simulation and theoretical analysis, the internal relation between the microscopic damage evolution and the macroscopic mechanical parameters will be revealed. Finally, based on the comprehensive research results, a fine macroscopic constitutive model for deep fractured rock mass deterioration under unilateral unloading condition is established. The research results can provide theoretical guidance for stability control and disaster control of mined out area.

深部金属矿山采空区失稳本质上是卸荷应力作用下围岩强度劣化引起的整体破坏，宏观表现为力学参数的弱化，细观表现为裂隙的扩展。目前岩体细观损伤与宏观力学参数弱化之间的内在联系仍不清楚，使得围岩强度劣化机制尚不明确。本课题以深部金属矿山采空区围岩为研究对象，围绕单侧卸荷条件下裂隙岩体细观损伤精细识别与定量表征、深部裂隙岩体劣化细宏观机制展开研究。首先针对含单组裂隙的岩体试样进行真三轴力学实验，研究裂隙岩体的宏观力学参数变化规律，同时利用核磁共振和电镜扫描技术，揭示细观损伤演化规律及空间分布特征，并建立基于核磁共振特征参数的损伤变量的定量表达式，结合图像处理技术进行三维重构，实现细观损伤的定位识别；然后结合细观数值模拟和理论分析，揭示细观损伤演化与宏观力学参数的内在联系；最后，综合研究成果，建立单侧卸荷条件下深部裂隙岩体劣化细宏观复合本构模型，研究成果可为采空区稳定性控制及灾害治理提供理论指导。

深部金属矿山采空区失稳本质上是卸荷应力作用下围岩强度劣化引起的整体破坏，宏观表现为力学参数的弱化，细观表现为裂隙的扩展。本项目围绕卸荷作用下裂隙岩体的细观损伤精细化表征、卸荷条件下岩体损伤劣化本构模型两个科学问题，综合采用现场调查、室内实验、数值模拟及理论分析等多种手段进行了系统、深入的研究。开展了深部金属矿采空区围岩节理裂隙调查及应力环境分析、单侧卸荷条件下深部裂隙岩体力学特性实验、裂隙岩体细观损伤精细识别与定量分析研究及卸荷条件下裂隙岩体强度劣化细宏观复合本构模型构建等研究工作，项目主要研究成果包括：（1）系统研究了三轴卸荷、真三轴动态卸荷、真三轴单侧卸荷过程中岩石的变形参数、强度参数、能量参数及损伤变量的演化规律，采用核磁共振扫描设备研究了T2谱参数演化规律及内部孔裂隙的扩展规律。建立了以T2谱参数面积为表征的损伤变量演化方程，考虑宏观应力及变形参数，建立了卸荷条件下裂隙岩体细宏观损伤本构模型，有效性验证表明，本项目建立的本构模型与室内实验结果存在较好的吻合度；（2）基于PFC细观数值模拟软件，对照室内实验条件，建立了真三轴单侧卸荷条件下的细观数值分析模型，针对不同裂隙岩石及卸荷条件下的岩石细观破裂机制进行了研究，揭示了细观内伤与宏观破裂之间的内在联系。本项目所取得的成果已在焦家金矿、蚕庄金矿及鑫汇金矿得到了应用，为企业的安全高效开采及采空区稳定性控制提供了理论依据，相关成果获得省部级科学技术奖一等奖2项。同时，在本项目资助下，共发表期刊论文16篇，授权专利9项，获得软件著作权2项，出版英文专著1部，成果技术转移1项。另外，培养人才9名，其中硕士毕业2名，在站博士后1人，在读博士1人。