Theoretical Study On Properties Of Soil And Structure During Pipe Jacking Construction

This paper relies on the construction of the rectangular pipe jacking project in the connection channel between Tuo-Dong gymnasium and Da-cheng Business District of Kunming Metro Line 6,combining on-site monitoring,theoretical calculation and numerical simulation,and conducting targeted research on the three-dimensional deformation of the stratum caused by the construction of large-section rectangular pipe jacking.The main research content and work include the following:(1)As a new type of underground space construction technology,Large Section Rectangular Pipe construction has higher requirements for construction technology.In order to achieve the purposes of safe and efficient construction,the selection of pipe jacking machinery,process flow and construction parameters are particularly important.Based on practical engineering,analysis the construction factors of large section rectangular pipe jacking,selected the method of construction parameters,construction process flow and related technical measures.From the construction results,the project has achieved better social and economic benefits.(2)The in-situ monitoring is made on the disturbance of soil induced by pipe jacking construction.The in-situ testing includes surface deformations,sub-surface movements,earth pressures,pore water pressures,underground water levels,SPT,stresses of pipes and pipe-soil contact stresses.In addition,the tatal jacking forces,deviations in line and level of the pipe line and earth pressures in the earth pressure balance machines are also recorded.The results of field-testing are analyzed,and the variety of testing datum include earth pressures,pore water pressures and underground water levels during the course of the shield through it are studied.(3)In order to find out the great differences of the surface subsidence caused by the difference of section type between the rectangular pipe jacking and the circular pipe jacking,This paper establishes a surface subsidence prediction model about large-size rectangular pipe jacking during the construction.this model are based on the three main controlling factors for surface subsidence caused by pipe jacking and Mindlin solution.Meanwhile,this paper make an intensive study of prediction model,empirical model and measured values using Matlab.The results show that the prediction method of surface subsidence has good agreement with the measured value at all stages of surface change,but the empirical model has a large difference with the measured value at the sedimentation sensitive area and the distribution law of surface subsidence is put forward.At the same time,the affected surface area is divided into four areas: uplift area,sedimentation sensitive area,settlement stable area and settlement subsidence area based on the strength of surface subsidence response.It provide theoretical guidance for similar projects in the future.(4)Based on the stress relief theory and the stress transfer theory,a formula for the peak value of the excess pore water pressure at any point induced by shield construction is deduced.(5)MIDAS GTS NX software is adopted to analyze actual project,mechanics characteristic and surface deformation in rectangular pipe jacking construction are analyzed.Results of calculation and monitor have relatively verified.Study the surface deformation caused by rectangular pipe jacking construction in different construction different construction parameter,different elastic module.