Study On The Influence Of Ground And Nearby Pile Foundation By Shallow Tunneling Under The Protection Of Pipe-roofing

In recent years,China's subway construction has developed rapidly.However,during the construction of subway tunnels,it will inevitably encounter some unfavorable working conditions,such as crossing the pile foundation or buildings(structures)at close range.Therefore,it is necessary to strictly control the ground subsidence and the deformation of adjacent buildings(structures)caused by the construction of subway tunnels.For the tunnel excavation by shallow undercutting construction method through the existing bridge pile foundation project,it is of great practical value to study the influence of different construction methods and advanced pre-reinforcement schemes on ground settlement and deformation of the existing bridge pile foundation.This article takes the underground excavation interval between Yuancun Station and Tianhe Park Station of Guangzhou Metro Line 21 as the research object,compares the theoretical calculation value,finite element calculation value and engineering measured value,and studies the influence of the construction of the subway tunnel under the condition of pipe-roofing reinforcement in Guangzhou area on the ground settlement and the adjacent pile foundation,the main research contents of this article are as follows:The main influencing factors of stratum deformation caused by shallow buried excavation method are summarized: stratum soil characteristics,groundwater,tunnel depth and cover ratio,construction method and supporting structure.The pipe-roofing reinforcement technology is introduced,and the role of the tube curtain is divided into three stages according to the mechanism of the pipe-roofing reinforcement area.Using MIDAS-GTS software,combined with the project overview and preliminary design plan,the impact of the presence or absence of pipe-roofing reinforcement on ground settlement was simulated and analyzed,and the relevant laws of ground settlement were obtained;by comparing the calculated value of finite element with the actual measured value of the project,it was verified the rationality of the model;By comparing the theoretical calculation value and the actual measured value,it is concluded that when the subway tunnel in Guangzhou area is constructed under the advanced reinforcement of the pipe-roofing,the ground settlement can be used when the settlement slot scale parameter is 0.76 and the formation loss rate is 0.35% Peck empirical formula for prediction.Based on a reasonable model,further explore the impact of construction on the pile foundation.By changing the advance reinforcement scheme of the shallow undercutting construction method tunnel,the distance between the pile foundation and the tunnel excavation centerline and the pile diameter,a variety of working conditions are set for different The displacement of the pile foundation under working conditions is analyzed.