Recovery of Cooling Water Circulation Tunnel Collapse: Construction of Permanent Bulkhead by Ground Freezing

In a power plant, two shield tunnels were constructed for circulating cooling water under the Yangtze River. During the construction of one line, a collapse occurred because of the abundance of methane in the ground. Artificial ground freezing (AGF) was adopted to recover the collapsed tunnel. A working platform was built above the river to facilitate ground freezing. The frozen soil wall (temporary ice bulkhead) formed in freezing was watertight and strong, providing temporary support before the concrete permanent bulkhead was constructed. This paper describes the design of chosen recovery option and the use of ground freezing which provides a safe environment for the permanent bulkhead construction and later works.