Construction of the vertical shaft between the undersea tunnel and the outlet

Upward excavation of a pilot shaft using the sealed type excavator

Abstract

In Shika Nuclear Power Plant Unit No.2, cooling seawater from the condenser is planned to be discharged through the undersea tunnel, as well as Unit No.1.
The vertical shaft between the tunnel tip and the outlet caisson was constructed from the tunnel. The pilot shaft was excavated upward from the tunnel to the outlet caisson after grouting, and then was expanded to diameter of 6m. A tightly water sealed type excavator was used to excavate the pilot shaft to ensure safety and workability.
This paper describes the results of upward excavation of the pilot shaft using the sealed type excavator.