Behavior of Twin Tunnels under Different Physical Conditions

Abstract

The deformation of twin tunnels was investigated under the influence of various physical conditions, namely, (1) mutual position and (2) change in the level of the water table, and the effect of using liners of different stiffness was assessed. The effects were defined in terms of settlement or deformation parameters suitable for tunnels. A detailed parametric study was conducted using the finite-element-based software Abaqus. The tunnels were assumed to be located within weathered granite rock, and the material properties were expressed in terms of equivalent cohesion and friction angle for rock. The liner was assumed to be elastic. A mathematical expression was proposed to quantify stiffness of the tunnel liner. All results are expressed in the form of nondimensional charts for better usability. Finally, two separate comparisons were shown to validate the modeling process. It is expected that the data presented in this note will help practitioners to understand and deal with the complex tunnel deformations associated with these field conditions.