It is difficult to ensure the stability of the tunnel structure due to large displacement under squeezing ground condition in conventional tunneling. Therefore, it is imperative to select the suitable tunnel cross-sectional geometry and support members according to the estimated ground pressure. Two-dimensional Finite Element Method (FEM) numerical analysis (GTS NX) was used to clarify the relationship between tunnel cross-sectional geometry and stress distribution in the support. The results of relationship between tunnel cross-sectional geometry and the specification of support confirmed that with the earth pressure increases, the stress concentration on support members could be decentralized by making the cross-sectional geometry circular. As a conclusion, the relationship of tunnel crosssectional geometry and the support stability could be established, and it shall be an indication for reasonable support design by using the numerical analysis.

1. Introduction

In conventional tunneling, it is difficult to ensure the stability of the tunnel structure due to large displacement under squeezing ground condition (Fig. 1). In this condition, the most effective way to control the deformation of the tunnel is by designing almost circular shape of tunnel section as well as installing highly rigid steel ring around the tunnel. However, as the shape of tunnel section become more circular, the volume of excavation increases hence inflicting high cost and longer excavation period. Therefore, it is imperative to select the suitable tunnel cross-sectional geometry and support members according to the estimated ground pressure. Since the standard design method under squeezing ground is yet to be established, numerical analysis method and case studies on the tunnel deformation are carried out, analyzed, and the characteristics of the stress occurred in the support were distinguished. This paper will be discussed the relationship between tunnel cross-sectional geometry and the specification of support.

2. Numerical Analysis
2.1 Analysis Method

In this study, two-dimensional Finite Element Method (FEM) numerical analysis (GTS NX) was used to clarify the relationship between tunnel cross-sectional geometry and stress distribution in the support.

This content is only available via PDF.
2019. Japanese Society for Rock Mechanics. Permission to distribute - International Society for Rock Mechanics and Rock Engineering
You can access this article if you purchase or spend a download.