Foundation Pit Deformation Control And Effect Evaluation Of Large Section Pipe-jacking Working Shaft

At present,pipe jacking technology has been applied in many projects in our country and maintained a momentum of rapid growth.There have also been breakthroughs in pipe jacking equipment and construction technology.However,there are few studies on largesection rectangular pipe jacking working wells,and The pipe simulation objects are mostly single pipe jacking.The research on double-line or multi-line pipe jacking is not yet complete,and there are few considerations of successive jacking and simultaneous jacking.At the same time,there is little attention to the impact of solids on the working well during the jacking process.For the reinforcement design of the active area of the pipe jacking project,the relevant design codes of our country have not made the latest instructions and regulations in time.Aiming at the above problems,this paper takes the large-section pipe jacking work well using bored pile technology as the research object in the south area,and mainly discusses the deformation of the backrest of the pipe jacking work well in the jacking stage and the reinforcement effect of solids behind the wall.The research content and results are as follows:(1)Taking the pipe jacking starting well as the object of investigation,according to the monitoring data during the construction of the pipe jacking work well,the deformation occurrence and corresponding change rules during the construction of the work well are analyzed.The monitoring results show that the area affected by the reaction force at the backrest during the jacking process is mainly located at the upper part of the pit bottom,and the back soil body "rebounds" during the unloading stage of the jacking pipe.(2)Combining the field measurement data,simulate and analyze the deformation during the construction of the pipe jacking shaft through finite element modeling.On the basis of verifying the feasibility of the finite element modeling and analysis,further analyze and demonstrate the effect of the ultimate thrusting reaction force.When the double pipes are jacked successively and simultaneously,the stress and deformation of the solid soil on the backrest of the working well and the corresponding stress and deformation characteristics of the pile wall,lining wall,and bottom plate of the working well.(3)Starting from the optimization design purpose,the finite element model was used to investigate the influence of the backrest plus solid size,the solid layout form,and the construction load around the working well.According to the analysis method of the influencing factors,the orthogonal test method was used to test the work Combination of backrest and solid dimensions,solid burial depth and material parameters are combined to evaluate the reinforcement effects of different reinforcement schemes,determine the order of influence of different factors,and provide relevant references for the optimization design and construction of large-section rectangular pipe jacking working wells.