| The m method in the two-dimensional elastic foundation beam analysis method is often used to analyze the force and deformation of the support system during the construction of the pile-inner support(anchor cable)foundation pit.However,there are two obvious defects in this method: First,the three-dimensional foundation pit and supporting system are simplified into a plane problem,and the interaction and spatial effect of all supporting piles,the ring beam(waist beams),inner supports(or anchor cables)and foundation soil cannot be considered;Second,according to experience,the proportional coefficient m of horizontal resistance of soil layer is given in advance,without considering the dynamic change of m value in the process of foundation pit construction.In order to overcome the above defects of m method,the supporting system(including supporting piles,inner supports(anchor cables),the ring beam(waist beams)and the foundation soil)of a foundation pit supporting surface is regarded as a pseudo 3-D co-actor in this artical,and with the pseudo 3-D co-actor as an object,using the optimization theory and foundation pit construction monitoring information,forward and back analysis methods of the force and deformation of support system at any construction stage were established firstly,then the methods were used to guide the informationization construction of foundation pit.The main achievements are as follows:(1)The forward analysis method of pseudo 3-D elastic foundation beam analysis method of the force and deformation of support system was established.This method firstly takes any single pile on the supporting surface as the research object,and establishes compatibility equations of force and deformation of a single pile in different construction conditions(excavation,setting up inner supports or pre-stressed anchor cables,applying prestress to anchor cables,etc.).Then,considering the synergism between the ring(waist)beam and the supporting pile,the research object is extended from a single pile to the whole supporting face,and then the equations of internal force and displacement are deduced,which simultaneously consider the excavation process,the setting of inner supports(oranchor cables)and the synergism of each supporting member.Finally,by solving the equations,the internal forces and deformation of the supporting piles,the ring beam(waist beams)and inner supports(or anchor cables)can be analyzed in the whole excavation process.(2)Taking the proportional coefficient m of the horizontal resistance of each soil layer as the parameter to be back-analyzed,and using the aforementioned forward analysis method and the horizontal monitoring displacement of the supporting pile during the foundation pit construction,the information construction problem of the foundation pit is firstly transformed into an objective function optimization problem of the back analysis of multiple proportional coefficients m.Then,by using Genetic Algorithm and Simplex Method in the optimization theory,the back analysis method of the Pseudo 3-D elastic foundation beam analysis method for the support system were established,which has the advantages of fast and accurate finding of the parameters to be back-analyzed.(3)The back analysis method was used to predict the force and deformation of the support system in the next construction stage of the foundation pit,and the informatization construction was preliminarily realized.(4)Applying the above information construction method to a practical project,the applicability and rationality of the proposed method are verified by comparing the predicted value of the method in the paper with the field monitoring value.(5)A calculation procedure of FORTRAN Language was compiled for the above analysis methods. |
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