Case Study: GK Immersed Tunnel Project

The GK Consortium is undertaking construction of an immersed tube tunnel, planned to be 3.7km in length. This project, in addition to other works in the area, forms one of the biggest civil engineering projects in Korea

As each of the tunnel units is sunk onto the seabed, the client required a concrete, or mortar, to fill gaps in the course of settling and fix the caissons and precast-concrete immersed tunnel

The client required a grout that is suitable for filling gaps between the caisson units and the seabed as they are sunk into position. The grout was to be suitable for pumping and placing underwater

Solutions were also required to repair the caisson units prior to them being placed on the seabed

Fosroc Korea proposed two grouting solutions, using materials that are suitable for pumping and placing underwater

Fosroc Conbextra UW is a pre-packaged underwater grout and Fosroc Conplast UW is an additive for site mixed grout. Both materials produce grouts that have anti-washout properties that enable placement underwater

A project team was set up by Fosroc Korea to assist the client in selecting the best solution. In addition to the local team, advice was obtained from Fosroc experts worldwide

Fosroc Repair & Remediation solutions were recommended and used for repairing precast concrete tunnel segments

Materials used included  Fosroc Nitofill EPLV, Fosroc Renderoc SPXtra / HB40 / HB60, Fosroc Conbextra GP, Fosroc Nitobond HAR

It is estimated that the project saved US$2m as a result of using the underwater grout additive and Fosroc concrete repair solutions