RAMP SHIELD TUNNELING EFFECTS ON AN EXISTING PARALLEL TUNNEL WITH 3D SEPARATION VARIATIONS

Abstract

 This paper studies the interaction effects between a newly excavated shield tunnel near the Baba entrance of the Metropolitan Expressway and the existing twin deep tunnels of the Yokohama Kita Line. It was a challenging issue to understand the influence of the proximity tunnel excavation of the Baba entrance on the existing main tunnels of the Yokohama Kita line.

 In this study, a three-dimensional numerical model of Baba entrance underground ramp is prepared. In the model, the excavation of new tunnel route is divided into four zones according to the (a) degree of tunnel alignment in vertical and horizontal directions, (b and c) volume and magnitude of grouting pressure, a prescribed displacement was introduced to the soil around the tunnel in each zone. The predicted lining deformation of existing main tunnels induced by new excavation was compared with the field measurement results. The proximity tunneling effects are discussed by using the comparison between the numerical simulation results and the field observations with the 3D variations of the separation in the twin tunnels.