(1. State Key Laboratory of Hydraulics and Mountain River Engineering，Sichuan University，Chengdu，Sichuan 610065，China；2. College of Water Resources and Hydropower，Sichuan University，Chengdu，Sichuan 610065，China)
Abstract：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 and 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.
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2012, Vol. 31 
