首先采用颗粒流程序(PFC)研究含马蹄形孔洞板状岩石模型在双轴压缩下的力学响应;其次,采用改进的复变函数法推导孔洞周边应力分布;最后,对锦屏二级水电站因岩爆引起的隧道破坏实例进行分析和讨论.结果表明,在低侧限应力作用下,孔洞周围共出现4种类型裂纹,即孔洞顶底板的初始拉伸裂纹、侧壁上的剥落裂缝、拐角处的次生拉伸裂纹和对角线上的剪切裂纹.随着侧限应力的增加,拉伸裂纹逐渐消失,而剥落破坏愈发严重.隧道模型的破坏现象与实际引水隧道的非常吻合,且解析获得的应力分布可以阐明裂纹的萌生机理.“,”A particle flow code (PFC) was first applied to examining the mechanical response of a horseshoe-shaped opening in prismatic rock models under biaxial compression. Next, an improved complex variable method was proposed to derive the stress distribution around the opening. Lastly, a case study of tunnel failure caused by rock burst in Jinping Ⅱ Hydropower Station was further analyzed and discussed. The results manifest that a total of four types of cracks occur around the opening under low lateral confining stress, namely, the primary-tensile cracks on the roof-floor, sidewall cracks on the sidewalls, secondary-tensile cracks on the corners and shear cracks along the diagonals. As the confining stress increases, the tensile cracks gradually disappear whilst the spalling failure becomes severe. Overall, the failure phenomenon of the modelled tunnel agrees well with that of the practical headrace tunnel, and the crack initiation mechanisms can be clearly clarified by the analytical stress distribution.