| In Japan, the application of closely spaced twin tunnels excavated by shotcrete method isincreasing. In order to construct closely spaced twin tunnels safely and rationally, it is required to establish thedesign method taking into full account the interaction between closely spaced twin tunnels. In this paper, analysison the field measurement data obtained at closely spaced twin tunnels construction sites was carried out and thefield measurement data were compared with the numerical analysis results using 3D and 2D finite different code.The results show that the influence of the second tunnel excavation on the first tunnel appears mainly as theincrease of the sectional forces in support structure at the sidewall on the second tunnel side and in some casessupport structure of both tunnels at the soil pillar side may support a load up to 80% of full overburden weight. |
