Reliability Analysis Of Combinatorial Supporting Structure Of Deep Foundation Pit Based On The Finite Element Method

In the foundation pit engineering, the traditional safety coefficient method takessoil as homogeneous material, and the properties of the parameters are determined. Itdoesn’t consider the actual natural variation value of the geotechnical parameter. It ishard to describe the characteristics of uncertainty in the foundation pit engineering. Inorder to consider the variability and uncertainty of the soil nature parameters andpractical environment in the foundation pit engineering and make the analysis resultsmore consistent with the practice, reliability analysis method in foundation pitengineering is develop gradually and used widely. Reliability analysis method usesprobability and mathematical statistics knowledge to analyze the variation of loadbearing capacity and the characteristic and law. According to existing engineeringexperience, it find the balance between the security and the economy. This foundationpit engineering stability evaluation method is based on the probability theory has a lotof advantages and becomes to be the development direction of the foundation pitengineering stability evaluation.The paper takes a deep foundation pit with combinatorial supporting structurewith anchor, pile and strut as research object. Analyze the reliability of combinatorialsupporting structure of deep foundation pit based on the finite element method. Thepaper simulates500times of the excavation process. According to the characteristicsof the foundation pit supporting structure and the soil properties, sets the failuremodes, gets the maximum horizontal displacement, pillar extraction settlement, thestrut axial forces, anchor of the axial force and random value and bar chart from thecalculation results, sets four failure criteria, and analyze structure reliability indifferent failure mode. With the aid of the basic theory of the structure systemreliability analysis, analyzes of the reliability of the foundation supporting structuresystem. Through the analysis of sensitivity identify influence of the supportingstructure reliability find the key variables.Main conclusions are as follows:(1) Through comparative analysis the result of finite element method simulation is in conformity with monitoring results. Therefore we can claim that this calculatingmodel is appropriate and supporting structure is safe.(2) According to the characteristics of the foundation pit supporting structure andthe soil properties, sets the failure modes, gets the maximum horizontal displacement,pillar extraction settlement, the strut axial forces, anchor of the axial force andrandom value and bar chart from the calculation results. The reliability is0.9544,0.937,1.0, and0.9970, respectively.(3) Takes supporting structure system as pillar settlement, strut axial forces andaxial force after anchor in parallel, and the maximum horizontal displacement in theseries mixed system. The reliability of the system is about0.95.(4) Weight has great influence on the reliability of the foundation pit structure.When weight increases the reliability decreases. The maximum horizontaldisplacement, pillar settlement and negatively related to the internal friction Angle,reliable level increases with the internal friction angle. The rest of the case sensitivityis not significant; its impact on the reliability can be ignored.