ABSTRACT
The Central Circular Shinjyuku Route of the Metropolitan Expressway is planned under the arterial road (Ring Road No. 6) in downtown Tokyo. The tunnel is planned to be constructed by the shield method, however the abandoned utility tunnel exists in the same alignment for about 1-km. Since the area is heavily congested and surrounded by the important structures, a conventional cut-and-cover method cannot be adopted to remove the existing tunnel. Thus, donut-shaped backfill shield is developed to remove the existing tunnel without causing adverse effects on the surface. Design of the back fill shield and the sequence of the existing tunnel removal procedure are introduced in this report.
