Effects of Pipe Roof Support and Grouting Pre-Reinforcement on the Track Settlement

Kui Wu,Zhushan Shao

doi:10.1155/2018/6041305

Kui Wu, Zhushan Shao

Open Access

https://doi.org/10.1155/2018/6041305

Copy DOI

Abstract

Based on the first shallow tunnel passing below an active railway station in the loess area in China, studies on the tunnel deformation and track settlement during tunneling are performed by using FLAC3D. It is found that, without adopting other reinforcement measures, the maximum track settlement has far exceeded engineering requirements. To reduce deformations induced by the tunneling, the combined presupport technique of the pipe roof and grouting reinforcement is presented and optimal construction parameters are provided. It is concluded that the installation of the pipe roof support plays an important role in controlling tunnel crown settlement and track settlement. The optimal pipe diameter is 159 mm, and the optimal arrangement area of the pipe roof is 150°. Grouting could improve soil strength and reduce deformations. The optimal thickness of the grouting reinforcement ring is 2 m. When the optimal parameters of the combined presupport technique are adopted, calculation results show that the maximum track settlement would reach 13.8 mm, which realized the settlement control goal of a maximum value of 15 mm. At last, the combined presupport technique proposed has been well validated in the “Railway Station” of Metro Line 4.

Highlights

In the past few decades, increasing demands on infrastructures increase attention on shallow soft ground tunneling methods in many urbanized areas
Hasanpour et al [12] investigated the effects of pipe roofing on surface settlements and evaluated the settlements associated with the twin tunnels in the Istanbul Metro by using numerical, semiempirical, and measured values
Based on the first shallow tunnel passing below an active railway station in the loess area in China, this paper deals with tunnel deformation and track settlement during tunneling by using FLAC3D

Summary

Introduction

In the past few decades, increasing demands on infrastructures increase attention on shallow soft ground tunneling methods in many urbanized areas. Many surface and subsurface structures make underground excavation works very delicate to the influence of deformation, which should be definitely limited to tolerable values [1]. E influence of underground construction on surface and subsurface structures should be accurately predicted, and corresponding remedial measures have to be put forward and taken prior to excavation. Suggested to use the pile-beam-arch method to control the surface settlement induced by metro tunnel excavation. For tunneling in the loess area, Zhao et al [17] systematically summarized the technical characteristics and main problems of the large-section loess tunnels in China’s speed railway, including classification of the surrounding rock, design of the supporting structure, surface settlement and cracking control, and safe and rapid construction methods. In order to meet engineering requirements, the combined pre-reinforcement technique is presented and optimal supporting parameters are further investigated. is paper could provide useful guidance for similar projects

Engineering Background and Numerical Model

III IV V VI VII

Grouting Pre-Reinforcement

Conclusions