中文摘要：

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。

英文摘要：

Deformation and fracture of brittle marble is closely related to the extension of internal microcracks,and the macroscopic mechanical response of marble depends on its mesoscopic structures. Because the micro cracks are sealed in rock bodies,it is very difficult to grasp the development mechanism of the internal microcracks. With the help of the three-dimensional theory of particle flow and introducing the BPM model and the technology of super unit clump,a mesoscopic structure model of marble in terms of the mineral configurations was established on the basis of the testing result of SEM on the mineral contents of marble from the underground powerhouse of Jinping I hydropower station. The mesoscopic mechanical parameters of marble based on the sensitivity analysis was determined according to the indoor testing results of the uniaxial and triaxial compression and the mesoscopic numerical model of marble was also constructed. The deformation and fracture and the expansion process of marble under different stress states and stress paths were analyzed through numerical simulations. The numerical results of the macroscopic mechanical response of marble were found to agree well with the laboratory testing results. The numbers of microcracks grew slowly initially and soon exponentially under the condition of uniaxial and low confining pressures,however,the growth curve was approximately an ＂S＂ shape under the condition of high confining pressure. As the increasing of the confining pressure,the proportion of the tensile cracks reduced gradually,and the shear cracks increased. Under the identical initial confining pressure,the axial strain at the peak strength of rock was smaller and the proportion of tensile cracks was higher in the unloading stress path than the ones in the loading stress path. The tensile cracks played the leading role in the unloading process and eventually caused the tensile macro fracture surface to be formed,indicated that the volume expansion effect of marble under unloading was more significa