Study on ground behavior by 4-centered slurry shield driving method

Roppongi station in Metropolitan Subway Route No. 12 is being constructed as vertical twin tunnels. Each tunnel is for the one track railway and the platform and is excavated by 4-Centered slurry shield. In order to make clear the influence of the second tunnel on the first one, model tests by using 1/50 scale shield model with cutting and mucking function were carried out. And to evaluate the influence of tunneling on the neighboring underground structures, 2D FEM analysis was carried out, taking account of the detailed construction process. As a result, the following was made clear: 1. The ground displacement is smaller when the upper tunnel is constructed first; 2. The earth pressure acting on the first tunnel due to the second tunnel is less than the overburden load with proper control of the mucking ratio; 3. The displacement of the existing structures is allowable by using MJS.