Research On Technical Performance Of Long Distance Curve Pipe Jacking Construction

With the development of urbanization,sponge city construction has been widely concerned as an effective means to reduce urban disasters.As a non-excavation construction technology,pipe jacking method has small environmental impact,short construction period and low comprehensive cost,which is widely used in the construction of sponge cities.This paper takes the long-distance curve pipe jacking project of the first water-spot reconstruction project of the Lvzhuxiang in Zhenjiang as the background.Through the simulation and theoretical calculation of the three-dimensional finite element software MIDAS-GTS,combined with the on-site monitoring data,the pipe jacking construction work is obtained.The law of influence of settlement and displacement of wells and surrounding roads is put forward,and the construction measures for controlling the top force and surrounding road settlement are put forward,in order to provide reference for similar pipe jacking projects in Zhenjiang area.The main research contents and results are as follows:(1)Study the influence of pipe jacking construction on the stability of working well and surrounding environment through three-dimensional numerical simulation.The analysis shows that for rectangular working wells with aspect ratio less than 2 and long side less than 10 m,the stability of beam element simulation support pile is closer to the actual construction conditions than the plate unit;secondly,compared with the top tube reaction force and the hole breakage For the stability of the working well,the former has a great influence,and the maximum increase of the deformation of the working well is 162%,and the settlement deformation of about 10 mm is generated around the working well;and the displacement increase before and after the hole is only 15%,so the top tube top should be emphasized.Adverse effects of pipe jacking force on the working well and surrounding environment during the process.(2)The influence of the jacking construction on the surrounding road settlement under different tunneling pressures,side frictional resistance and additional loads is studied by three-dimensional numerical simulation.The results show that the additional load changes have obvious influence on the surrounding road settlement,and the tunneling pressure is second,and the side friction resistance has almost no effect.Under the same conditions,the larger the upper additional load,the greater the disturbance of the soil around the design axis by the pipe jacking construction.When the upper load is 0kN/m2 and 25kN/m2,the peak displacement generated by the pipe jacking construction is about 20 mm.With the increase of tunneling pressure,the pipe jacking construction has less influence on the degree and extent of soil disturbance around the axis than the additional load.When the tunneling pressure is theoretically calculated as the active earth pressure 120 kPa,the numerical simulation results are closest to the actual monitoring value.It shows that the numerical simulation is close to the theoretical calculation value,and the finite element analysis has high reliability and has certain engineering value.(3)According to the physical properties of the pipe through the soil layer,considering the influence of the additional top force of the pipe jacking pipe,the total top force of the Y-6 to Y-4 curve pipe jacking and the force of the adjacent pipe joints in the curve section are obtained through theoretical analysis.Compared with the allowable top force calculation of the reinforced concrete used in this project,the top force control measures of the pipe jacking construction are proposed,including the inter-relay setting and the external pipe grouting reduction to ensure the integrity and continuity of the pipe jacking process.(4)Based on the top force theory calculation and analysis results,the number of layouts between the relays of the project is calculated by analyzing the top force segmentation of the position between the relays,and combined with the analysis of the top force monitoring data,it can be formed when the pipeline is externally formed.When the whole mud set is used,the side friction resistance of the pipe and the mud sleeve is less than the recommended value of 4 kPa in the technical regulations for the pipe jacking of the water supply and drainage project.At the same time,the grouting mix ratio and grouting amount calculation formula suitable for the geological conditions of the project are given,which provides reference for similar pipe jacking projects in Zhenjiang area.(5)Through the on-site test method,the problem of “steamed head” after the jacking of the deep silt area is proposed and solved,including the method of strengthening the double-tube high-pressure jet grouting pile at the outer hole of the working well;secondly,from the perspective of on-site construction technology Starting,by controlling the jacking speed after the jacking of the jacking pipe and using the tie rod to connect the jacking tool tube with the front pipe joint to prevent the occurrence of the jacking phenomenon of the jacking pipe.