Study On The Initial Supports' Reliability Of Deep Buried Tunnels

The initial supports'reliability of deep-buried tunnels, which constructed in weak surrounding rock environment with New Austrian Method, determines the safety and efficiency of subsequent construction procedures. The initial supports'reliability has to do with many uncertainties such as rock quality, construction method, when initial supports being constructed after the excavation, which kinds of materials being used in initial supports, and so on. As a common practice, in-situ monitoring and surveying information being used to judge the stability of surrounding rock, it is a passive method to judge the correctness of the designed initial supports'plan. As the uncertainties of surrounding rock effects the designed initial supports'reliability greatly, how to simulate these uncertainties is the highest priority of this study. Monte Carlo Method could be used in such situation, the statistical characteristics might be found by many times'simulation with reasonable random value of rock parameters. Contents and resulting achievements of this paper are as follows:â‘ Many different methods used in structural reliability analysis were thoroughly discussed in this paper. The validity of these methods when being used on the initial supports'reliability analysis was being compared.â‘¡Different kinds of methods used to produce quasi random numbers were discussed in this paper. Methods to check the statistical characteristics of those produced quasi random numbers have introduced in this paper. As the complementary sampling technique is more efficient than direct sampling method during the Monte Carlo simulations, the complementary sampling technique were used in the initial supports'reliability analysis of deep buried tunnels in this paper.â‘¢Two different methods modeling the role of rock bolt in FEM models have being studied and compared in this paper. The methods to simulate the surrounding rock's unloading after excavation in FEM model simulation were being worked out and developed special program with APDL programmer's Language.â‘£Three different methods to establish the state function of initial supports'utmost state were being compared in this paper. During the comparison, supporting role exaggeration of line element, which used in FEM model to simulate the initial lining and rock bolt, were being found in FEM simulation. Line element reaction forces which were greater than usual were reported in FEM analysis results.