深部地下洞室施工期围岩大变形机制分析

大岗山水电站引水发电系统地下洞室埋深大,花岗岩因风化卸荷强烈,岩脉破碎带发育,应力较高。在施工过程中,岩脉、断层穿越的主变室部位出现较大的变形,严重影响施工安全与进度。采用地质调查和现场监测的方法,结合现场施工情况分析主变室围岩大变形特征和机制,提出2种可能的大变形破坏模式,分析影响围岩大变形的因素,并评价主变室的稳定性。研究结果表明:主变室围岩大变形主要受辉绿岩脉8 1和断层f59,f60控制,同时,地应力高、施工强度大、支护进度滞后加剧围岩的大变形。深部地下洞室施工期的地质调查及现场监测可以及时预测高应力区卸荷围岩的大变形,以确保洞室施工期的稳定安全。研究成果对类似工程具有重要的参考价值。

LARGE DEFORMATION MECHANISM ANALYSIS OF SURROUNDING ROCKS IN DEEP UNDERGROUND CAVERN DURING CONSTRUCTION

The underground caverns of Dagangshan hydropower station show typical characteristics of large buried-depth,strong weathering of surrounding rocks,full development of dike and fractures,and high in-situ stresses.During construction,the deformation of transformer chamber where dikes and faults cross through is very significant,which seriously affects the safety and advance of construction.On the basis of geological investigation and field monitoring,according to the field construction condition,the large deformation mechanism of surrounding rocks is analyzed.Two possible large deformation failure modes are proposed.Factors inducing large deformation are analyzed,and the stability of transformer chamber is evaluated.The results show that the large deformation of surrounding rocks is mainly controlled by diabase dike 8 1and faults f59,f60.The high in-situ stresses,high intensity of construction and delayed supporting accelerate the large deformation of surrounding rocks.The geological investigation and field monitoring are very useful for forecasting the large deformation of unloading rocks in high stress zones,and for ensuring the stability and safety of underground cavern during construction.The results have very important reference values for similar projects.