Numerical analysis of the interaction between twin-tunnels: Influence of the relative position and construction procedure

The development of transportation in large cities requires the construction of twin-tunnels or the construction of new tunnels close to the existing ones. Since, both the relative position of tunnels and the construction procedure affect the soil movement and internal forces in the lining, it is of major interest to study the influence of these factors on the tunnel design. This paper presents analysis of this issue with a particular interest for the optimization of both the relative position of the twin-tunnels and the construction procedure. For this concern, a parametric study is conducted for the investigation of the influence of these two factors on the soil settlement and internal forces resulting from the tunnel construction. The paper presents successively the numerical model and then analyses conducted for three configurations of the twin-tunnels: aligned-horizontally, vertically and inclined. It shows that the construction procedure affects the soil settlement and internal forces. The construction of upper tunnel at first leads to both higher settlement and bending moment. The highest soil settlement is obtained for vertical aligned tunnels, while horizontal aligned tunnels cause the lowest settlement.