Ground Deformation Characteristics Induced by Mechanized Shield Twin Tunnelling along Curved Alignments

Dangzhong Wu,Kang Cheng,Xiaonan Gong,Gang Lei,Kaiping Xu,Panpan Guo,Junhong Yuan

doi:10.1155/2021/6640072

Abstract

This paper investigates the ground deformation characteristics induced by mechanized shield twin tunnelling along curved alignments by adopting the nonlinear three-dimensional (3D) finite element method (FEM). The performance of the adopted FEM is demonstrated to be satisfactory by comparing the numerical analysis results with the field monitoring data in a typical case history and with the predicted results generated by a modified version of the Peck’s empirical Gaussian formula. It has been found that the tunnelling-induced transverse ground surface settlement troughs and the distributions of the subsurface horizontal and vertical ground displacements are mostly similar in both form and magnitude for the considered various radii of curvature of tunnel alignment including 50 m, 100 m, 150 m, 200 m, 250 m, 300 m, 400 m, and infinity (i.e., straight-line tunnel). Considering the variational characteristics of the ground deformations with the magnitude of the radius of curvature, the radius of curvature of 100 m can be regarded as a critical tunnel alignment radius of curvature controlling the transformation of the curved tunnelling-induced ground deformational behaviors. For the benefit of geotechnical engineers interested in curved tunnelling with a small radius of curvature, a discussion of the technologies for reducing the overexcavation and improving the accuracy of tunnel lining segment installation is also presented.

Highlights

Tunnels play an important part in the development of economics and society, and they have many uses such as transportation, including canals, trains, metros, road vehicles, etc., for mining ores, and for conducting sewage and water [1,2,3]
E construction procedure for mechanized shield tunnelling method includes four repeated steps: tunnel boring machine (TBM) advancement by thrust of hydraulic jacks, soil excavation by cutterhead, ring segment installation, and synchronous tail void grouting. ese steps involve a complex interaction between TBM and the surrounding soil, which controls the behavior of the tunnel structure as well as the impact of the tunnelling process on the surrounding ground and facilities
Considering the small magnitudes of the radius of curvature and the cover depth, the ground deformations induced by shield twin tunnels need to be estimated accurately for the protection of the structures adjacent to the considered case history

Summary

Introduction

Tunnels play an important part in the development of economics and society, and they have many uses such as transportation, including canals, trains, metros, road vehicles, etc., for mining ores, and for conducting sewage and water [1,2,3]. Depending on the considerations of various factors such as geological conditions, environmental impacts, construction cost and period, and tunnel dimensions, a tunnel may be excavated using one of the commonly adopted methods including mainly the cut-and-cover method [7, 8], drill-and-blast method [9, 10], mechanized shield tunnelling method using a tunnel boring machine (TBM) [11, 12], new Austrian tunnelling method [13, 14], and jacked box tunnelling method [15, 16] Among these methods, the mechanized shield tunnelling method has been widely used for constructing metros in many urban areas in the world [17,18,19]. A discussion of the critical stability guarantee technique is presented to provide reference for geotechnical engineering practitioners

Case History

Numerical Modelling

Results and Discussion