Stability Study Of Deep Foundation Pit Support Structure Based On Reliability Analysis Method

In the study of foundation pit engineering,the former method of calculating the safety factor through the classical soil mechanics assumes that the soil mass is a homogeneous material with constant and definite parameters of isotropic properties.Such assumption ignores the discrete variation of geotechnical properties in the actual engineering,which will lead to the uncertainty of foundation pit engineering itself can not be described in this way.The classical soil mechanics method can only evaluate the supporting structure,but not form a quantitative evaluation.In view of the problems that can not be ignored in the stability analysis of foundation pit and the problems that are not intuitionistic in the stability evaluation of foundation pit,the method of reliability theory arises at the historic moment.The results of this method can show the variability of soil,which is more in line with the actual situation.So far,reliability and uncertainty analysis methods have developed very mature.In the field of structural design,the standard system based on reliability theory has taken the lead in forming,but the research and application of uncertainty analysis theory system in geotechnical engineering is not complete.1.Three expressions of reliability are analyzed: reliability probability,failure probability and reliability index;Several methods of reliability calculation are introduced,including first-order second-moment method,monte carlo method and JC method.2.With stochastic finite element method,the generalized stochastic finite element numerical method based on fuzzy random,based on the decomposition theorem of fuzzy space [X](A ?(L P ?)?)on fuzzy variational theory,and then based on the principles of expansion in generalized uncertain space Ο:(S,F)on the proposed fuzzy random variable such;Based on the classical stochastic finite element theory,the march-past of random variation establishes a linear once-approximation stochastic finite element model,and constructs three membership functions of M in the theory domain of structural safety state in geotechnical engineering.3.Based on the fuzzy random variation theory and the expansion principle,the reliability calculation model of foundation pit engineering stability is established,and the formula is derived.Based on this calculation model and formula,the reliability calculation of foundation pit supporting engineering of the underground parking lot of chifeng hospital is carried out.4.Use Flac 3D finite element calculation software to establish the calculation model of the foundation pit of the underground parking lot of chifeng hospital and simulate the excavation process.According to the supporting characteristics of this project and the soil properties of the site,the maximum horizontal displacement of supporting structure,settlement of supporting pile,supporting axial force,anchor cable axial force and other values are calculated.5.According to the theoretical calculation structure,the calculation results of finite element software and the actual monitoring results,the sensitivity analysis of each random variable was carried out.The results show that the stability of the foundation pit is guaranteed by the synergistic action of supporting pile and anchor cable.The results show that the theoretical model is suitable.