Application Of Stochastic Finite Element Method In Deep Excavation Reliability Calculation Based On Secondary Development Of ABAQUS

With the development and utilization of urban construction and underground space,more and more complex deep excavation projects emerge one after another.As a common form of deep excavation support,the internal bracing structure of row piles requires high stability and small deformation.The traditional design method of retaining structure of deep excavation adopts fixed parameters and does not fully consider the variability of material parameters.Therefore,it is more scientific and closer to actual practical engineering to use the method of reliability calculation to evaluate the stability and deformation of the supporting structure.Firstly,the reliability theory method and its application in deep excavation engineering were interpreted.Then,on the basis of Monte Carlo stochastic finite element method,the finite element simulation software Abaqus/CAE was redeveloped by using Python programming language,and the purpose of calculating the reliability of antioverturning stability and deformation reliability of the supporting structure was realized.In order to verify the effectiveness of present method,three parameters,which were soil weight,internal friction angle and cohesion force,were taken as random variables to calculate the reliabilities of a deep excavation.Besides,using this method,the influence of geometrical size of supporting structure,the water table lever in excavation area and the erection position of interbracing on the reliability index of deep excavation were studied.The main contents are list as follows:(1)The concept of reliability,reliability evaluation index,commonly used reliability calculation method,distribution types and numerical characteristics of random variables were introduced.Then,the application and research progress of reliability analysis theory and finite element method used in deep excavation were summarized.The deficiency of current research was analyzed,and the main research contents were put forward.(2)Based on the Monte Carlo stochastic finite element method,the secondary development of Abaqus /CAE finite element simulation software was carried out to achieve the function of random sampling and bringing the sample value into the CAE model for cyclic calculation.Then,the ODB file was used to extract the calculation results,and the corresponding result samples were obtained by using the algorithm.After statistical analysis on the result samples,the reliability of anti-overturning stability and deformation reliability of the supporting structure were calculated according to the approximate probability method.The results show that the secondary development technology can not only calculate the deformation reliability,but also calculate the stability reliability of the supporting structure.(3)The influence of the geometrical parameters of the supporting structure on the reliability index were studied by changing the pile diameter,embedding depth and the erection position of the interbracing separately.The fluid permeability-stress coupling analysis method provided by Abaqus was used to investigate the influence of the water table level in the excavation area on the reliability index.The results show that the larger diameter of the supporting pile,the lower position of the interbracing and lower water table level in the excavation area,have better deformation reliabilities of the supporting structure.Besids,the upper position of the interbracing,the smaller horizontal span of the interbracing and lower water table level in the excavation area,have better antioverturning stabilities of the supporting structure.The results obtained in present dissertation can provide reference for the design and optimization of deep excacation.