Research On The Mechanical Effect And Construction Optimization Of The Pipe Shed Under The High-speed Railway Foundation

With the construction of three-dimensional traffic in cities,there are increasing numbers of large-surface shallow-buried traffic tunnels.For crossing the busy roads and railways,the method which jacking frame bridge with the protection of pipe jacking has a wide range of applications due to is small impact on surface environmental.This article is based on the Engineering that Nanchang New Longgang Avenue which is under the Xiangpu Railway.According to the characteristics of large pipe diameter,long installation length,and large jacking section in the Engineering,theoretical analysis,experimental research,field measurement and other methods are adopted.In this construction method,the determination of the reasonable spacing of pipe shed,the mechanical effectiveness of pipe shed,and the rational optimization of parameters in pipe shed construction have been deeply studied.The main research contents are as follows:(1)Check the relevant materials and literatures to understand the construction theories and construction techniques of the application cases related to pipe shed engineering at home and abroad,then make a simple comment on the research status of the application of pipe shed.(2)Based on the theory of micro soil arching of anti-slide pile in the foundation Engineering,combined with the characteristics of the horizontal pipe shed to make appropriate assumptions about the micro-arch structure,the micro-arch analysis model was established.Then the control equation of the allowable spacing of the pipe shed was deduced by using the Coulomb Moore criterion as the intensity damage criterion.Through the equation,the maximum allowable spacing of the pipe shed is determined in the case of determining the diameter of the pipe shed and the parameters of the soil material,to ensure the soil on the pipe shed is stable and then prove its rationality through its application in practical Engineering.At the same time,the effects of the diameter of pipe shed,the cohesion of soil,the angle of friction in soil and the coefficient of friction of pipe soil on the maximum allowable spacing of pipe shed were further discussed.(3)Based on the Winkel Ground Beam Theory,the effect of pipe shed pre-supporting was analyzed.The appropriate assumptions based on different excavation conditions during construction was established,and then the corresponding formula was obtained to study the effect of unloading and overloading of the pipe shed.When settlement occurs in the pipe shed,the pipe shed can transfer the weight of the overlying soil,bear the corresponding load,and reduce the earth pressure on the excavation surface.When the truss jacking of the frame bridge produces bulging,the pipe shed has the effect of suppressing the bulging of the ground.At the same time,the influence of various factors on the supporting effect of pipe shed was analyzed,and through the application in the actual Engineering to prove its reasonableness.(4)For the correlative experiment of setting up pipe shed in actual Engineering,the analysis of fishbone diagrams and the identification of relevant reasons were made to find out the cracking of roadbeds in the experiment.Then the thick-walled hole theory was used to optimize the construction parameters of the drilling and the field measurement methods was used to optimize the process of the steel drag,to ensure that the large-diameter and long pipe shed can be smoothly passed through the high railway foundation.Finally,based on the research results of this paper,the author made some suggestions for similar Engineering at home and abroad.