Study On Construction Disturbance And Deformation Control Of Large Diameter Pipe Jacking Under Box Culvert In Soft Ground Layer

In recent years,China’s rapid urbanization process,many water supply and drainage,communication,electric power and other municipal pipeline projects need to be built,and with the popularity of municipal pipeline network and the increasing demand,various types of underground pipelines are intertwined,and the construction scale of underground pipeline network,the construction environment and construction difficulties faced are increasing.In this thesis,we take a 4m net diameter pipe jacking project of a wastewater treatment plant in Shanghai as background,and use a combination of theoretical analysis,numerical simulation and field measurements to carry out a systematic study on the construction process of large diameter pipe jacking in soft ground and its construction disturbance and deformation effects of underpassing existing underground box culvert,establish a mechanical model of pipe jacking-soilbox culvert interaction based on small hole expansion theory,reveal the interaction mechanism between pipe jacking and surrounding strata and The mechanism of interaction between pipe jacking and surrounding stratum and adjacent underground structure is revealed,and the force deformation law of pipe jacking,stratum and existing box culvert is obtained during the whole process of pipe jacking construction,and the construction parameters of pipe jacking and existing box culvert reinforcement measures and methods are optimized.The main research contents and conclusions of this thesis are as follows:(1)Based on the small hole expansion theory,the mechanical model of pipe jacking-soil-box culvert interaction is established,the influence of different pipe jacking burial depths and different excavation surface support forces on the evolution of soil stress and deformation field as well as box culvert structure is analyzed,and the law of interaction between pipe jacking construction disturbance and existing box culvert structure is clarified.(2)Based on the finite element method,a three-dimensional numerical calculation model considering soil loss and excavation surface support force is established to analyze the influence of disturbance of large diameter pipe jacking construction on the adjacent box culvert in soft ground in Shanghai.(3)Integrating the theoretical analysis and numerical calculation results,the optimization analysis of parameters such as soil shrinkage rate and excavation surface support force during pipe jacking construction was completed,and the control measures of disturbed deformation of large-diameter pipe jacking construction were proposed.(4)Comprehensive numerical calculation and field measurement results,continuous observation of pipe sheet force,ground surface and box culvert settlement in the actual construction process,the results show that the actual construction of the jacking pipe joint butt quality and jacking jack loading state has a greater impact on the pipe sheet force,the jacking pipe construction to cross the box culvert below the increase in the wall after the grouting pressure can effectively reduce the disturbance of the jacking pipe construction on the existing box culvert structure.