The cracked chevron notched Brazilian disc method (CCNBD) recommended by the International Society for Rock Mechanics is a major method for measuring the rock fracture toughness. In the rock fracture mechanics, the micro-crack evolution behavior during Mode I fracture is of great theoretical significance. To fully understand the micro-crack evolution mechanism and fracture process zone evolution information of non-uniform sandstone, numerical simulation of CCNBD specimen under Mode I fracture condition was carried out using PFC^3D. Combined with the box fractal dimension theory, the sandstone particle size and mineral composition were considered, and the non-uniform bonded particle model was built. By monitoring the evolution of micro-cracks in the interior and boundary of the cluster, the micro-crack evolution process of the numerical model was obtained. The results showed that the micro-fracture of CCNBD specimen during the cracking process was dominated by weak cementation plane and the contact of interstitial filling particles, while the micro-crack generated between detritus particles mainly concentrated in the CCNBD specimen with the peak stress range of 80–100% and the post-peak failure stage. Combined with the stress field analysis, the Mode I fracture experiment of the bonding between diagenetic mineral particles at the crack tip of CCNBD specimen was dominated by tension, while the bonding between interstitial filling particles is dominated by compression. The micro-crack evolution mechanism of the CCNBD specimen during Mode I fracture was obtained by experiments and numerical simulations. This study is expected to improve the understanding of the unstable fracture mechanism of the fractured rock mass.

国际岩石力学学会推荐的裂纹人字形缺口巴西圆盘法（CCNBD）是测量岩石断裂韧性的主要方法。在岩石断裂力学中，I型断裂过程中的微裂纹演化行为具有重要的理论意义。为全面了解非均匀砂岩微裂纹演化机制和断裂过程带演化信息，利用PFC ^3D对Mode I断裂条件下CCNBD试件进行数值模拟. 结合盒分形维数理论，综合考虑砂岩粒度和矿物成分，建立非均匀粘结颗粒模型。通过监测团簇内部和边界微裂纹的演化，得到数值模型的微裂纹演化过程。结果表明，CCNBD试件在开裂过程中的微裂缝以弱胶结面和填隙充填颗粒的接触为主，而碎屑颗粒之间产生的微裂缝主要集中在CCNBD试件中，峰值应力范围为80-100% 和峰值后失效阶段。结合应力场分析，CCNBD 试件裂纹尖端成岩矿物颗粒之间的结合以拉力为主，填隙颗粒之间的结合以压缩为主。通过实验和数值模拟得到CCNBD试样在I型断裂过程中的微裂纹演化机制。该研究有望提高对裂隙岩体不稳定断裂机制的认识。