Extreme Wave Monitoring and In Situ Wave Pressure Measurement for the Cofferdam Construction of the Pingtan Strait Bridge

Cofferdams used in the coastal area have shown severe damages after typhoons including fracture of the steel piles, overturn and even total collapse. In order to enhance the understanding on the met-ocean conditions of the site and the wave pressure on the wall of cofferdam, extreme wave elevation was obtained through ultrasonic wave measuring instrument and wave pressure around the cofferdam were measured by 15 wave pressure gauges at 2 different water levels during Typhoon Dujuan (2015) swept across the bridge site. The measured wave elevations were analyzed with statistical method. Actual distribution of hydrodynamic pressure on the cofferdam was obtained from the measured wave pressures. Wave pressures on the cofferdam under regular wave were calculated by diffraction analyses using commercial hydrodynamic software ANSYS AQWA. The numerical simulation results were validated by the measured pressure on the cofferdam. The main conclusions of this study are: (1) extreme waves induced by typhoon Dujuan had reached the design wave height for the cofferdam, which might threaten the construction safety; and (2) diffraction analyses based on AQWA gives reasonable wave pressures, which allows for a faster preliminary evaluation of cofferdam.