Abstract: Seawall is the first barrier against typhoon storm surge for coastal areas and islands in Zhejiang Province. Cutting through broad areas, seawalls are severely affected by bad climate in typhoon period with rapid internal response to external influence. In view of this, a remote real-time dynamic monitoring technology for seawall safety is presented with features of large coverage, distributed monitoring and centralized management. The real-time monitoring technology was applied to the standard seawall at Yancang of Haining City in Qiantang River, as well as Wanzhang seawall of Zhoushan City in east Zhejiang. Monitoring results show that the inner water level of seawall obtained through seepage pressure gauge is well related to tide level, and the effect of tidal level fluctuation on seepage gradually weakens from the inside to the outside of seawall. The internal hydraulic gradient of seawall is within allowable value, guaranteeing seepage stability. Moreover, horizontal deformation at millimeter level would occur under the action of tide. With the tide level fluctuation, internal horizontal displacement of seawall changes cyclically. In particular, the horizontal displacement of the upper part of seawall is greater than that of the lower part. The real-time monitoring results provide technical support for routine maintenance and emergency treatment of the seawall.

Key words: typical seawall in Zhejiang Province, typhoon storm surge, real-time safety monitoring, water level obtained by seepage pressure gauge, horizontal deformation