| Because the engineering properties of tunnel is distinctive. Leading to the stress deformation and failure of tunnel structure are often complex, changeable, and affected by many factors. And these influence factors usually come from load, material, geometry etc of tunnel structure. Most of these factors are random variables, include numerous uncertainties.With the development of theoretical study and engineering technology, the theoretical results which were based on certainty showed some irrationality. Experts and scholars carry out a large number of basic works of the random variable which has a relationship with the tunnel structure, and get the probabilistic design methodology limit based on the reliability theory.With the vigorous development of Chinese construction of the tunnel, the large deformation disaster in the weak surrounding which is harm, high treatment costs and high construction risk has become a major problem plagued underground engineering, meanwhile, it is a large subject that need to be overcome quickly by engineering researchers.This paper introduced structural reliability and the large deformation theory of weak surrounding at home and abroad, summarized the structural reliability and soft rock large deformation theory which is based on the relevant literature and research. Then the Tian Chiping tunnel has been chosen to be simulated the continuous tunnel excavation stage construction process in two-dimensional by the ANSYS, besides taking into account the effects of surrounding rock, supporting structural materials which can influence the stochastic properties of the tunnel, try to change time random into wall rock disturbance factor. Making shifting function and the ultimate limit state equation contained time random calculate reliability of each step and research stochastic properties during the excavation by using Monte-Carlo method. In the excavation process of each step, the elastic modulus of surrounding rock is the greatest impact on the settlement of tunnel vault, and with the increase of the elastic modulus of rock, the arch crown settlement(negative) increases; The thickness and the elastic modulus of the supporting structure impact the vault settlement less than the elastic modulus of surrounding rock, and both of them increased with tunnel vault settlement(negative) increased; The random characteristic of the surrounding rock density has little effect on the vault settlement, with the increasing density of the surrounding rock tunnel vault settlement(negative) decreased. The above rules are unchanged in the process of tunnel excavation.But after the completion of the tunnel excavation, the thickness and the elastic modulus of the supporting structure on the effect of vault settlement rather than impact on the displacement of surrounding rock in density. This is contrary to the law of tunnel excavation.the influence of supporting structure during tunnel excavation on tunnel stability is greater than that of tunnel excavation. It also proves that the random characteristic of the supportingstructure is more important to the tunnel stability during the tunnel excavation. So in the excavation process of large deformation of soft rock tunnel in the initial supporting structure construction of tunnel structure and surrounding rock stability is significant. But no matter in the process of tunnel excavation and tunnel after excavation, the influence of surrounding rock modulus on the settlement of tunnel vault is the greatest. So the uncertainty of surrounding rock is the main reason for the tunnel structure reliability in the process of tunnel excavation. |
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