| The pipe jacking method is an important part of the undercut method and is widely used in the excavation of underground pipelines in my country.In the pipe jacking construction,the thrust reaction force generated by the pipe jacking is mainly borne by the pipe jacking working shaft and the soil behind the well.Traditional working shafts mostly use cement structures,which have disadvantages such as high construction cost,long cycle,large pollution and difficult recovery.This paper proposes a new type steel-polymer composite assembly type recyclable pipe jacking work shaft supporting structure,and its structural stability is analyzed.The details are as follows.(1)Analysis of the advantages and disadvantages of common work shaft support forms,combined with the analysis theory of support structure and design calculation methods,puts forward the design ideas of new work shafts.(2)A three-dimensional finite element model of the jacking pipe is established,and the pile spacing,waist beam spacing and the size of the rear seat wall of the supporting structure are analyzed and calculated in combination with the orthogonal design method.By calculating the allowable jacking force of the working shaft and the mechanical response of the working shaft under the action of jacking pipe jacking,the stability of the supporting structure is analyzed and the design scheme is determined.(3)Carry out on-site full-scale tests,real-time monitoring of the force of each structural component of the working shaft during the construction process.The measured results are compared with the numerical simulation results to further analyze the force characteristics of the working shaft.And verified the rationality and accuracy of the finite element model.(4)Aiming at the needs of complex engineering,a numerical model of parallel double jacking pipes in the same working shaft was established.The two pipes are pushed in one after the other.The working shaft and soil conditions disturbed by the construction of the first pipeline are taken as the initial state of the second section of pipeline jacking.The structural stability of the working shaft under two jacking actions is analyzed,and the mechanical response of the working shaft under repeated jacking forces is analyzed and verified by field tests.(5)Analyze the force and deformation of the soil around the working shaft,the force and deformation of the working shaft under different jacking forces and friction forces,and the impact of 131m long jacking pipe jacking on the working shaft.The feasibility and safety of the working shaft in single jacking and repeated jacking are verified.(6)Clarify the position and change rule of the larger value of the stress displacement of the working shaft during the jacking of the pipe,and combine it with the real-time monitoring data on site.The numerical model of the pipe jacking working shaft is analyzed,verified and perfected,which provides a theoretical basis and scientific basis for the future application of the steel-polymer composite assembly support structure in the pipe jacking. |
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