The Study on Wave-Induced Failure Mechanisms of Vertical Seawalls during Typhoon Periods

• Main Authors: Chen, Da-Wei, 陳大煒
• Other Authors: Tzang, Shiaw-Yih
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/49645935824030476660

博士 === 國立臺灣海洋大學 === 河海工程學系 === 103 === This study investigates wave-induced similar failure mechanisms of vertical seawalls of National Taiwan Ocean University (NTOU) and Pa-Tou-Tsu (PTT) in coastal waters of Keelung by the same typhoons. Typical damages include break-off of parapets of NTOU original seawalls, breaking and backward displacements of concrete coverings of rear bulk structures and associated drainage ditches for both rebuilt seawalls. By summarizing historical photos of damages first illustrate that damages can be categorized into three failure modes. They consist of distributions of impact wave pressures on the seaside of vertical faces (Mode 1), the kinematic behaviors of overtopping waves (Mode2), and hydrodynamic poundings of wave overtopping (Mode3). It is thought to be attributed to violent typhoon waves on higher surges and intense hydrodynamic behaviors of wave overtopping. Then numerical simulations on hydrodynamic behaviors by a modified mesh-free Smoothed Particle Hydrodynamics scheme show that the raised storm surge levels with great instantaneous wave impacts on the higher vertical faces resulted in damages on the parapets and concrete coverings of drainage ditches right behind the parapet (Mode 1). For Mode 2, the lower crest height or higher waves could increase the influenced distance and overtopping flow poundings on top of the seawall. For Mode 3, peak values of landward jet velocity by down-falling overtopping waves have occurred behind the parapets. The other peaks of landward jet velocity could be generated when the overtopping waters enter into shallower flooding water upon top of seawalls but decrease with deeper flooding. The simulated interactions on top of the seawalls between overtopping flows and a moving object indicate that the driving forces decreases with deeper flooding while broken concrete coverings were displaced due to large wave overtopping.