中文摘要：

黄河上游拉西瓦水电站大型地下厂房洞群，主体工程开挖完工后，位于主厂房与主变室之问的母线洞围岩产生环向裂缝，类似现象在龙滩、二滩、广蓄、大朝山等水电站地下厂房工程中也已出现多次。对其成因进行分析研究对后续处理措施与加固方案的设计具有根本性指导意义。以拉西瓦水电站大型地下厂房为例，结合工程类比，分析裂缝宏观特征；以数值试验为手段，对裂缝的成因进行详细分析探讨。研究结果表明，母线洞围岩在地下厂房结构中特殊的位置，导致其在施工过程中逐渐形成特殊的应力状态，致使其出现环向裂缝；地应力分布是裂缝出现的重要客观因素。最后，对类似的地下厂房工程，提出支护措施设计的几点建议。

英文摘要：

The underground cavern group of Laxiwa Hydropower Station is one of the largest projects in China at present. When the excavation is completed, a number of splits appear in surrounding rock of busbar tunnels. There are similar phenomena in Longtan, Ertan, Guangxu, Dachaoshan Hydropower Stations. Finding the reason of this phenomenon is helpful for strengthening the stability of caverns. For this instance, Laxiwa Hydropower Station is taken for example to study causes of this phenomenon and get the reasonable reinforced measures. At first, the corresponding characteristics of the splits are found by comparing different projects. Then the process that splits come to being is studied with numerical simulation methods. The results indicate that the especial position of busbar tunnels in the powerhouse can result in stress concentration on parts of surrounding rock of busbar tunnels and then splits come into being. Meanwhile, it can be found that geostress is another important factor for the splits. Finally, several reinforced measures are put forward for similar projects.