The deployable element, a new closure joint construction method for immersed tunnel

A new closure joint construction of immersed tunnel, the deployable element, was developed in Island and Tunnel Project of Hong Kong-Zhuhai-Macao Bridge. The method shortens installation time at sea, enables positive connection and waterstop under water, and makes the work reversible. In this paper, the author presents the concept and critical issues of design and construction of this method. Further, its improvements for future application were discussed.