Abstract:Considering the difficulty of setting up the performance function in structure reliability analysis of large complicated underground cavern,a calculation method on the structure reliability that combines 3D non-linear finite element method,response surface method,and JC method,is established. Based on the calculated results that use different quantile values of 8 random parameters by 3D non-linear finite element method and D-P criterion,the reliability function of underground cavern is deduced. Then,the response surface function,the stress component partial derivative function,and the random parameter partial derivative function of both wallrock and the umbrella arch,are also achieved. At last,the reliability index is calculated by JC method. The method is applied to the cavern structure reliability analysis of the underground powerhouse of Yingxiuwan hydropower station in Sichuan province that has been operated for mo re than 30 years. It shows that the value of b is between 1.5 and 4.8,which,as a whole,is on the low side. Most of the low value of b lies in the area of left side of the axial line,where is the main cracking area. By comparing with the monitoring data,it shows that the method can get good precision,high performance,and well practicability. The new method is proved to be a good means in the structure reliability analysis of large underground cavern and other complicated hydrostructures.