Three-Dimensional Numerical Investigation of the Interaction Between Twin Tunnels

Abstract

The construction of twin tunnels is an obligatory guideline and a prevailing practice in either conventional or mechanized tunneling. Nevertheless, most of the design methods for calculating the tunnel loads focus on single tunnels, thus, neglecting the potential interaction between neighboring tunnels. The effect of such interaction can be signi cant, especially for closely-spaced twin tunnels. In this context, this paper investigates via parametric 3D Finite Element (3D-FE) analyses the interaction between deep, parallel-twin, circular and non-circular tunnels excavated with a conventional (non-TBM) method and supported with shotcrete lining. The numerical investigation focuses on the axial forces acting on the primary support of the tunnels by examining the effect of a wide range of geometrical (pillar width, overburden height, tunnel diameter and section (shape), lagging distance), geotechnical (strength and deformability of the surrounding rockmass, horizontal stress ratio), structural (thickness and deformability of the shotcrete lining) and construction parameters (full-or partial-face excavation and support of the tunnels). The results of the analyses indicate that the construction of the subsequent tunnel in uences the loads of the precedent. The stress state of the single tunnel is used as the reference for the quanti cation of the interaction effect. The output is presented in normalized design charts of the quanti ed interaction effect on the axial forces, versus key geomaterial and geometry parameters to facilitate preliminary estimations of primary support requirements for twin tunnels.

Parametric Investigation of Interaction between Soil-Surface Structure and Twin Tunnel Excavation: A Comprehensive 2D Numerical Study

“…Additionally, the study explored the impact of the distance between two symmetrical structures relative to the tunnel axis, the weight of the structure, and the presence of one or two structures located above the tunnels. In recent years, various numerical and analytical studies have been conducted to explore the impact of twin tunnel excavations on surrounding structures and soil [16][17][18][19][20][21][22]. For instance, Duangsano et al [16] investigated the effect of twin tunnel excavation on structures located on pile foundations in the case of the Bangkok MRT Orange Line.…”

“…However, their study was limited to the green field scenario without considering the presence of surface structures. Furthermore, Chortis and Kavvadas [20] studied the interaction effect between twin tunnels by analyzing the impact of each tunnel on the internal forces of the other. Cavalcanti et al [21] compared two-dimensional numerical analysis with semi-empirical methods to calculate subsidence resulting from twin tunnel excavation in green field conditions.…”