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脆性大理岩的变形破裂与其内部微裂纹的扩展贯通密切相关,其宏观力学响应取决于细观结构构造;因岩石内部的封闭性,难以掌握其内部微裂纹的发育演化机制。基于三维颗粒流理论,通过引入BPM模型和超级单元clump技术,并依据锦屏一级地下厂房大理岩的SEM矿物成份检测结果,建立基于矿物形状的大理岩细观结构模型,在对细观力学参数敏感性分析的基础上,根据室内单轴和三轴压缩试验结果确定大理岩的细观力学参数,构建大理岩的细观力学数值模型,对不同应力状态和应力路径下大理岩的变形破裂演化及扩容孕育过程进行数值模拟分析。研究结果表明:大理岩细观力学数值模型所描述的宏观力学响应与室内试验结果具有很好的一致性;单轴或低围压时微裂纹呈缓慢–急增的指数型增长趋势,高围压时微裂纹呈缓慢–急增–缓慢的近似S型增长趋势;随着围压的增加,张拉裂纹所占比例逐渐减少,剪切裂纹所占比例逐渐增加;与相同初始围压时的加载应力路径相比,卸载应力路径下岩石峰值应力对应的轴向应变小,张拉裂纹所占比例高,且随卸载过程逐渐起主控作用,最终形成张性宏观破裂面,体现了大理岩卸荷扩容效应更为显著且脆性更强。在不同应力状态和应力路径下,张性裂纹扩展控制机制和剪切裂纹摩擦控制机制相互作用,此减彼增逐步过渡。研究结果从细观尺度上揭示锦屏一级大理岩扩容孕育机制,为正确认识和把握锦屏一级地下厂房洞室群施工期围岩大变形形成机制以及岩体卸荷破裂规律提供基础。
The deformation and fracture of brittle marble are closely related to the expansion and propagation of microcracks. The macroscopic mechanical response depends on the structure of meso-structure. Because of the closed nature of the rock, it is difficult to grasp the mechanism of the microcrack development. Based on the three-dimensional particle flow theory, by introducing the BPM model and the super-unit clump technology, and based on the results of the SEM mineralogical detection of the marble of the underground powerhouse of Jinping I, the marble shape model of the marble based on the mineral shape is established, Based on the sensitivity analysis of parameters, the meso-mechanics parameters of marble are determined according to the uniaxial and triaxial compression tests in indoor. The mesomechanical numerical model of marble is established. The deformation and fracture of marble under different stress states and stress paths Evolution and expansion of the nurturing process for numerical simulation analysis. The results show that the macroscopic mechanical response described by the numerical model of marble meso-mechanics has a good agreement with the indoor test results. The microcracks show a slow-increasing exponential growth trend under uniaxial or low confining pressure. With the increase of confining pressure, the proportion of tensile cracks decreases and the proportion of shear cracks increases gradually. With the same initial confining pressure Compared with loading stress path, the peak stress of rock under unloading stress path is corresponding to small axial strain, high proportion of tensile cracks and gradual mastering action with the unloading process, finally forming macroscopic macroscopic rupture surface, Unloading dilatation effect is more significant and more brittle. Under different stress states and stress paths, the tension crack growth control mechanism interacts with the shear friction control mechanism. The results reveal the mechanism of capacity expansion and gestation of Jinping-grade marble from a mesoscopic scale, which provides a basis for correctly understanding and controlling the formation mechanism of surrounding rock large deformation and the unloading and rupture during the construction of the cavern group in Jinping-A underground powerhouse.