Natural fracture data from one of the Carboniferous shale masses in the eastern Qaidam Basin were used to establish a stochastic model of a discrete fracture network and to perform discrete element simulation research on the size effect and mechanical parameters of shale. Analytical solutions of fictitious joints in transversely isotropic media were derived, which made it possible for the proposed numerical model to simulate the bedding and natural fractures in shale masses. The results indicate that there are two main factors influencing the representative elementary volume (REV) size of a shale mass. The first and most decisive factor is the presence of natural fractures in the block itself. The second is the anisotropy ratio: the greater the anisotropy is, the larger the REV. The bedding angle has little influence on the REV size, whereas it has a certain influence on the mechanical parameters of the rock mass. When the bedding angle approaches the average orientation of the natural fractures, the mechanical parameters of the shale blocks decrease greatly. The REV representing the mechanical properties of the Carboniferous shale masses in the eastern Qaidam Basin were comprehensively identified by considering the influence of bedding and natural fractures. When the numerical model size is larger than the REV, the fractured rock mass discontinuities can be transformed into equivalent continuities, which provides a method for simulating shale with natural fractures and bedding to analyze the stability of a borehole wall in shale.

利用柴达木盆地东部石炭系页岩块的天然裂缝资料，建立离散裂缝网络的随机模型，对页岩的尺寸效应和力学参数进行离散元模拟研究。推导了横向各向同性介质中虚拟节理的解析解，使所提出的数值模型能够模拟页岩体中的层理和天然裂缝。结果表明，影响页岩体的代表性基本体积（REV）大小的主要因素有两个。第一个也是最具决定性的因素是地块本身存在天然裂缝。二是各向异性比：各向异性越大，REV越大。层理角度对 REV 大小影响不大，而对岩体力学参数有一定的影响。当层理角接近天然裂缝平均方位时，页岩块体力学参数大幅度下降。综合考虑层理和天然裂缝的影响，综合确定了代表柴东地区石炭系页岩体力学性质的REV。当数值模型尺寸大于 REV 时，裂隙岩体不连续面可以转化为等效连续面，为模拟天然裂缝和层理页岩分析页岩井壁稳定性提供了一种方法。当层理角接近天然裂缝平均方位时，页岩块体力学参数大幅度下降。综合考虑层理和天然裂缝的影响，综合确定了代表柴东地区石炭系页岩体力学性质的REV。当数值模型尺寸大于 REV 时，裂隙岩体不连续面可以转化为等效连续面，为模拟天然裂缝和层理页岩分析页岩井壁稳定性提供了一种方法。当层理角接近天然裂缝平均方位时，页岩块体力学参数大幅度下降。综合考虑层理和天然裂缝的影响，综合确定了代表柴东地区石炭系页岩体力学性质的REV。当数值模型尺寸大于 REV 时，裂隙岩体不连续面可以转化为等效连续面，为模拟天然裂缝和层理页岩分析页岩井壁稳定性提供了一种方法。综合考虑层理和天然裂缝的影响，综合确定了代表柴东地区石炭系页岩体力学性质的REV。当数值模型尺寸大于 REV 时，裂隙岩体不连续面可以转化为等效连续面，为模拟天然裂缝和层理页岩分析页岩井壁稳定性提供了一种方法。综合考虑层理和天然裂缝的影响，综合确定了代表柴东地区石炭系页岩体力学性质的REV。当数值模型尺寸大于 REV 时，裂隙岩体不连续面可以转化为等效连续面，为模拟天然裂缝和层理页岩分析页岩井壁稳定性提供了一种方法。