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

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.

Ground Displacements due to the Deformations of Shallow Tunnels with Arbitrary Cross Sections in Soft Ground

“…where w(ζ) is the conjugate of the complex function w(ζ), ζ is a complex variable in the ζ-plane, ζ � ξ + iη � ρe iϑ , ξ and η are variables of the Cartesian coordinates system in the mapped plane, and ρ and ϑ are variables of the polar coordinates system in the mapped plane. From (7), the stress components can be obtained as follows:…”

“…In the last twenty years, a variety of special-shaped shields have been developed to build tunnels with many different shapes and cross sections [1][2][3][4][5][6][7]. Compared with the most widely used circular tunnels, noncircular tunnels are believed to have the advantage of making full use of excavated space [8].…”

Internal and External Collapse Analysis of Twin-Tubes Tunnel in the Initial Support Stage

“…The soil deformations and the modifications created by the stresses of the soil during the digging of the tunnel, are closely linked with the digging technique. [1,2]. The basic principle of tunneling with the new Austrian method is to have the rock transported by itself.…”

Observed Performance and FEM-Based Parametric Analysis of a Top-Down Deep Excavation in Soil-Rock Composite Stratum

“…In the past several decades, extensive studies have been conducted to investigate the performance of deep excavations in terms of excavation-induced deformation and internal force characteristics of retaining walls and bracing structures [9][10][11], ground movements [12][13][14], and response of preexisting structures that are adjacent to the excavations [15][16][17]. These studies are based mainly on numerical simulations [18,19], empirical or semiempirical methods [20,21], analytical solutions [22,23], in situ monitoring data analysis [24,25], centrifuge or scaled model testing [26,27], and machine learning [28,29].…”