Analysis Of Stability And Influencing Factors Of "Dual-purpose Pile Wall" Enclosure Structure

Since the development of underground space and foundation pit engineering until2021,people have put forward higher and higher requirements for environmental protection and energy saving,safety and stability,economic cost,space area,etc.of the project,which cannot be satisfied by traditional temporary support.In the continuous exploration of,the "dual-purpose pile wall" supporting structure came into being.Although this structure has been applied and developed in foreign countries for decades,foreign scholars lack in-depth research on this structure;and there are few applications of this structure in China,including Hefei.Therefore,there is still a lack of theoretical research on the new supporting structure system at home and abroad,and there is no clear design method and theoretical calculation method in the relevant domestic literature and codes.At present,a small number of related researches on this structure have been applied in China,and because of regional differences,there are great differences in design methods and theoretical research.There is still a lot of room for growth and exploration in the feasibility and technical details of the "dual-purpose pile wall" structure.By reading a large number of domestic and foreign related literature and typical cases,the author carefully grinds and summarizes,and further summarizes the specific classification and design summary of the "dual-purpose pile wall" structure.And through the combination of specific engineering cases,the specific working state of the new type of "dual-purpose pile wall" support structure is deeply discussed,the stability and superiority of this structure are proved,and the design method of the new structure is further proposed through the finite element theory.I hope to make my own efforts for the wide application and promotion of the "dual-purpose pile wall" enclosure structure.The main contents and achievements of this paper are as follows:（1）Summarize the application status and development history of foundation pit engineering and the combination design of enclosure structure and main structure,put forward some current problems,and give the original research intention and main technical content of this paper.（2）Summarize the main design forms of the "dual-purpose pile wall" support structure,start from the different ways of combining the main structure and the support structure,make specific classifications,and comprehensively summarize all the new types of support structures that have appeared at present.And compares it with the most common traditional temporary supports listed,and expounds the fundamental difference and function difference between permanent support and temporary support.On this basis,this paper focuses on the design principle of the "dual-purpose pile wall" structure without intermediate fulcrum.（3）Combined with the deep foundation pit project of a rainwater regulation and storage tank in Hefei,MIDAS three-dimensional finite element software was used to simulate,and a finite element model including the main structure,support structure and force transmission structure was established to refine the undisturbed soil stage.The whole process of construction conditions including the excavation stage of the foundation pit,the construction of the main structure,the layout stage of the force transmission plate and the permanent use stage,and the construction conditions of the enclosure pile,outer wall and inner support during the excavation process of the foundation pit are studied.The internal force and displacement deformation laws are compared with the actual monitoring data to verify the correctness of the established model and the feasibility of the structure.（4）Through the finite element simulation of the "dual-purpose pile wall" structure in all working conditions,the internal force（bending moment,shear force）and deformation（deep horizontal displacement）of the ground connecting wall and basement exterior wall in the model at different stages are specifically analyzed.According to the changing situation,the load sharing mode of pile-wall two-in-one structure is expounded.Compared with the results of the finite element model of the traditional structure,it is proved that the stability,economy and environmental comfort of the permanent structure of the enclosure pile are much better than those of the traditional structure,and it is necessary to further popularize and apply it.Finally,the optimal reasoning on the design rules that can be carried out by the new support structure is obtained.（5）Aiming at the design method of the new supporting structure of "dual-purpose pile wall",in order to verify the conclusion of this paper on the optimization reasoning of the design rules,the method of controlling a single variable is used to change the structures such as the retaining piles,the outer wall,and the force transmission strip.Factors such as thickness,length,stiffness,spacing,etc.observed the internal force and deformation trend of the enclosure piles and the basement exterior wall,and obtained specific operation suggestions for the combination of enclosure piles and exterior walls in the structural design method.It fully demonstrates the economical and energy-saving characteristics of permanent fencing piles.Figure[60] table [1] reference [54]...