Construction Sequence Optimization and Settlement Control Countermeasures of Metro Tunnels Underpassing Expressway

Chengzhong Zhang,Junbao Wang,Ziming Pei,Zhanping Song,Qiang Zhang,Zhushan Shao

doi:10.1155/2021/8834368

Chengzhong Zhang, Junbao Wang + Show 4 more

Open Access

https://doi.org/10.1155/2021/8834368

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Abstract

The Chongqing metro line 6 underpass expressway around the city is taken as an engineering background, and the optimal excavation sequence and corresponding control countermeasures for the triangular-distributed three-line metro tunnel underpass expressway are studied. The influences of excavation sequence on the tunnel surrounding rock deformation, surrounding rock stress, supporting structure stress, plastic zone, and surface settlement are analyzed by using MIDAS/GTS NX finite element software. The numerical simulation results showed that Case 1 is the optimal excavation sequence of the metro tunnel. However, the surface settlement under the optimal excavation sequence exceeds the limit value of 30 mm, which cannot guarantee the safety of expressway traffic. On this basis, the control measure for strengthening the three-line tunnels with advanced small pipe grouting and reinforcing the middle tunnel with concrete-filled steel tube piles are proposed. Moreover, the excavation process of the metro tunnel with and without reinforcement schemes is numerically simulated. The results show that the reinforcement scheme can effectively control the surface settlement value within the limited value (16.47 mm), which is close to the maximum surface settlement of 18.31 mm after the metro tunnel excavation is completed, indicating that the proposed reinforcement scheme is beneficial to ensure the safety of metro tunnel construction and the driving safety of the expressway.

Highlights

Built metro tunnels underpassing through the upper existing buildings and traffic lines are common engineering problems in urban infrastructure construction [1,2,3]
During the construction of metro tunnels, it is very easy to cause large surface settlement, which will threaten the safety of existing buildings and traffic lines on the upper part [4,5,6]. erefore, it is necessary to study the impact of metro tunnel construction on the existing buildings and traffic lines and the corresponding construction control countermeasures [7,8,9]
In this paper, relying on the project of Chongqing metro tunnel line 6 underpassing through the expressway around the city, numerical simulation methods are used to study the surrounding rock deformation, surface settlement, and stress distribution of the supporting structure of the threeline metro tunnels with a triangular distribution under different excavation sequences, and the optimal excavation sequence is determined

Summary

Introduction

Built metro tunnels underpassing through the upper existing buildings (structures) and traffic lines are common engineering problems in urban infrastructure construction [1,2,3]. Based on the Chongqing metro tunnel line 6 underpassing through the expressway around the city, the MIDAS/ GTS NX numerical simulation software is used to simulate the surrounding rock deformation, supporting structure stress distribution, and surface settlement of the metro tunnel under different excavation sequences, and the optimal excavation sequence is determined. On this basis, the control measure for strengthening the three-line tunnels with advanced small pipe grouting and reinforcing the middle tunnel with concrete-filled steel tube piles is proposed, and the numerical simulation of the metro tunnel excavation process with and without reinforcement schemes is carried out

Project Overview and Construction Difficulties

Analysis of Numerical Simulation Results

Conclusions