中文摘要：

块体是结构控制型岩体中常见的潜在危险源之一。利用极限平衡法及强度折减法两种方法计算了某在建特大型水电站地下厂房开挖揭露的部分块体的安全系数,并根据计算结果提出一种利用块体几何及力学参数判断其稳定性的简便图解方法,经现场监测数据验证计算结果可靠性可满足工程要求。研究表明,对同一块体而言,极限平衡法和强度折减法得到的安全系数以及对其稳定性的总体判别结果并不一致。强度折减法受软件算法及网格尺寸影响,结果偏于保守。简单块体的安全系数计算应以极限平衡法为主,而复杂形态块体的安全系数用强度折减法计算较为方便。利用垂向地应力、块体体积、最大角点深度及结构面等效强度等4个指标并结合块体稳定性判别分区图,可满足快速判断块体稳定性的需要。对于判别为不稳定的块体,应及时支护并考虑加强支护。研究成果可用于类似工程块体稳定性的快速分析。

英文摘要：

Blocks are one of potential failure modes appeared mainly in structurally-controlled rock mass.Factors of safety（Fo S） for blocks identified in underground caverns of a huge hydropower station are obtained using the limit equilibrium method and strength reduction method.A simple graphical method for stability analysis based on block parameters is proposed by the calculated Fo S of the block,and the reliability of results is validated by in-situ monitoring data.It is found that the Fo S values obtained by these two methods are inconsistent even for the same block,which thus further influence the stability judgment.Results obtained by the strength reduction method are conservative since it is affected by software algorithm realization and mesh sizes.Fo S of simple blocks（i.e.blocks consist of 3 joints and excavation boundary） can be easily obtained by the limit equilibrium method,while Fo S of complex blocks（i.e.blocks consist of more than 3 joints and excavation boundary） are more conveniently calculated by the strength reduction method.Four block parameters,namely vertical in-situ stress,block volume,the maximum vertex depth,and equivalent joint shear strength,in combination with the stability partition chart,are applied to assist in the stability judgment.Once blocks are determined as unstable,the proper support and reinforcement measures should be adopted promptly.These findings can be used to other cases with similar unstable problems of blocks.