Ground Freezing Application of Intake Installing Construction of an Underwater Tunnel

The abstract: In a power plant in China, two shield tunnels including east line and west line were planned to construct for circulating cooling water under the Yangtze River. During the construction of the east line, a collapse occurred which destroyed the tunnel section originally designed for intakes. Decision was made to abandon the collapsed section of the tunnel and the intakes would be built in the adjacent section of the tunnel that remained intact. Unlike conventional intake construction technology scheme of jacking the intake pipes from the tunnel inside vertically upward to the river, the new scheme was adopted to install the intakes from the river surface down to the inside of tunnel. Artificial ground freezing (AGF) method was firstly applied to provide a safety condition of intake installing construction, which played a role of water sealing and soil reinforcing. A freezing and monitoring system had been set up on the working platform above river to control and monitor the temperature of the soil around the intakes to realize the engineering reliability. This paper describes the technique of AGF and the intake installation procedure of this project, briefly analyzing the temperature field of frozen soil around intakes. The result show that the development of frozen curtain is under control and AGF was successfully applied to the intake installing construction of this underwater project with a favorable effect. The engineering application might be important for reference in other underwater tunnel projects.