The Study Of Failure Model And Design Method Of Shallow Buried Tiinnel

Finite element strength reduction method has got rapid development, and it hasbeen widely used in slope engineering. The practice proves that the theory has astrong applicability. In recent years, Zheng Yingren, Hu Wenqing and others havebegun to introduce the theory to apply in tunnel engineering, and put forward theconception of safety factor of tunnel, which can quantify the stability of the tunnel.The traditional finite element method can not be used to calculate the safety factor andfailure of surrounding rocks of tunnel, only by the stress, displacement, stress andplastic zoenes are unable to accurately judge the tunnel failure surface; the classicallimit analysis method can be applied to engineering design but poor adaptability.However the strength reduction finite element method based on the reduction of rockand soil mass strength parameters,which leads rock and soil mass to a limit state, sothat it comes out potential failure surface.This method not only can calculate thesafety factor but also widely used in engineering practice.Based on the strength reduction finite element principle, and by numericalanalysis software,the failure model of tunnel, shallow buried tunnel looseningpressure, and bias tunnel failure modes were discussed in this paper. This atrticalcombines numerical analysis and model test to discuss shallow buried tunnel damagemodel, and analysed four kinds of different conditions, the results show thatnumerical analysis and model test results are quite close, using numerical analysissoftware to analyze the failure model and safety coefficient of tunnel is feasible.This paper presents two kinds of shallow soil loosening pressure calculationmethod, one is based on FEM limit analysis theory, adding reverse node force on thetunnel arch bottom, and by regulating the force so that the model is in the state oflimit equilibrium. The method has strict mechanical basis, and without assuming thefailure surface. Considering external adverse conditions, soil strength parametershould be reduced, the calculation results are more close to the actual situation,itprovides a new method to solve the problem of shallow soil tunnel loosening pressure.Another one is the modified rock column theory, which considers external adverseconditions as well, and the overlying soil strength parameters should be reduced, thetunnel top loose pressure is produced by vault above soil.This paper uses numerical limit analysis method to simply discusses bias tunnelfailure model, rupture surface appears at the arch of shallow side of the bias tunnel, rupture surface developed in the direction to ground surface. local destruction appearsat small grade．Tunnel excavation makes great influence on slope stability，at the samedepth，the slope geade is more greater，the stability coefficient is more smaller andmore weaker．...