Research On Construction Mechanics Effect And Risk Assessment Of The Shallow Bias Tunnel

With the implementation of the western development strategy, and the rapid development in highway transportation, the construction of mountain road tunnel in the western is presenting a brilliant situation.The quantities of tunnel increase fast,and encountered more and more technical problems.This paper combines Zuan Qianmen tunnel in Shanxi Province, and takes it as the project background. Through the theoretical analysis,field measurement and finite element numerical simulation method, the paper studies and explores the construction mechanics of shallow buried bias tunnel and its risk assessment of excavation. The research of this paper is as follows:â‘ According to analyse the results of monitoring measurement, indicated maybe the phenomenon of steel arch's unevenly stressing is the results of terrain bias.â‘¡Build 18 numerical models in conditions of different minimum safe thichness of over burden, different land slope, different geological conditions by means of finite element analysis software ANSYS. Analyze and summary the stress of tunnel,first timbering,second timbering,and the displacement condition.â‘¢This paper analyzes the relationship between stress points on yield surface and not, then puts forward the concept of load effect coefficient (LEC),at last derives the function of LEC based on Drucker-Prager criterion.Load effect can be quantitative described by LEC,and tunnel can be determined the sequence of stress damage by the value of the different regions'LEC.â‘£The result of 18 examples suggests the stability of tunnel can be measured by the effect of asymmetrically loaded and the load effect of surrounding rock. In this thesis,BBN is applied in risk analysis model for shallow buried bias tunnel using BBN software Netica. In order to get cases for parameter in BBN(Bayesian Belief Network),18 FE examples are calculated. This risk analysis model is also applied to some interesting fields,such as probability inference,most probable explanation and sensitivity analysis.Calculated results indicate this model is fit for real project.