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A particle method, or a gridless Lagrangian method, shows the high performance in describing the complicated behavior of water surface with the fragmentation and coalescence of water. In this paper, a wave overtopping process on a vertical seawall is numerically simulated on the basis of the Navier–Stokes equation with surface-tension term, which is discretized by the MPS (moving particle semi-implicit) method belonging to the category of the particle method. An improvement of the listing process of neighboring particle is introduced to reduce the computational load. Wave overtopping process in the experiments are well reproduced by the MPS method. The predictions of the MPS method of the overtopping volume agree well with the experimental results.

This study investigates the changes in coastal topography of the Rikuzen-Takata Coast in Iwate Prefecture, Japan before and after the 2011 off the Pacific coast of Tohoku Earthquake Tsunami and the effects of coastal structures on these changes. The changes in coastal topography were analyzed using bathymetry data and aerial photographs before and after the tsunami in addition to aerial video during the tsunami. The bathymetry data were obtained from 1989 to 2002 during the construction of three submerged breakwaters and from after the 2011 tsunami until 2013. The aerial photographs were acquired from 1947 to 2015, and the aerial videos were acquired during the tsunami run-up and backwash. The results demonstrated that the coast was eroded mainly due to the tsunami backwash, and the submerged breakwaters trapped the seaward transport of sediment from the coast. Erosion was partly prevented in locations where the seawall was not washed away. The coastal structures had significant effects on the behavior of the coastal tsunami and on sediment transport. We also found that the coast did not recover naturally at the desired speed after the tsunami because the coast had been stable before the tsunami. Coastal restoration five years after the 2011 tsunami are also summarized in the Appendix to illustrate the future reconstruction plan for the study coast.

This study proposes a safety evaluation process for a prevention structure against tsunamis, in which the most updated guideline (i.e. FEMA P-646) is used as the deterministic analysis and a probabilistic approach is adopted to consider uncertainties involved. To overcome the incomplete data on Tsunamis, a Markov chain Monte Carlo (MCMC) simulation is developed to increase the quantity of historical data from Taiwan followed by the use of the least squares support vector machine (LS-SVM) to estimate the probability density function (PDF) of random variables. Based on the fragility analyses of the superstructure, substructure and entire system, if the wall thickness is below 4.45m, the wall thickness is more likely to be the governing factor compared with the pile diameter. Conversely, the pile diameter would more likely be the dominating factor. When the pile size decreases from 75cm to 65cm, the threshold value will shift from 4.45m to 3.85m. In addition, when the wall thickness and height are greater, there is a greater likelihood of the failure probability being governed by the substructure. Based on historical records only, the probability of failure of the seawall is extremely low. Nevertheless, results shown here are in line with the engineering judgement and the computation procedure established in the present study can be used as a reference for performing safety analysis on tsunami structures with insufficient data.

Seawall is a most commonly used structure in coastal areas to protect the landscape and coastal facilities. The studies of interactions between the tsunami-like solitary waves and the seawalls are relatively rare in the literature. In this study, a three-dimensional numerical model based on OpenFOAM® was developed to investigate the tsunami-like solitary waves propagating over a rectangular seawall. The Navier–Stokes equations for two-phase incompressible flow, combining with methods of $k-\epsilon$ for turbulence closure and Volume of Fluid (VOF) for tracking the free surface, were solved. Laboratory experiments were performed to measure some of the hydrodynamic feature associated with solitary waves. The model was then validated by the laboratory data, and good agreements were found for free surface, velocity and dynamic pressure around the seawall. Finally, a series of numerical experiments were conducted to analyze the evolution of both wave and flow fields, the overtopping discharge as well as wave pressure (force) around the seawall, special attention is given to the effects of seawall crest width. Our findings will help to improve the understanding in the occurrences of tsunami-induced damages in the vicinity of seawall such as wave impact and local scouring.

This study focuses on the application of structured cementing technology in the marine environment, which is based on self-compacting cement-based materials and underwater self-protecting casting cementing technology. In this study, cylindrical samples of structuralized cemented stone columns are developed in the laboratory to test material strength and other key features related to the material. Following this line, extensive numerical experiments are conducted to investigate the interaction between in situ sea mud and cemented stone column-seawall systems. The methods developed in this study will provide a technical basis for understanding the behavior of the newly invented cemented stone column-seawall system from a numerical perspective.

Simulative analyses were carried out to study the effects of sea level rise (SLR) and global climate change scenarios on storm tide levels fronting the Roxas Boulevard seawall. Storm tides under historical typhoons and various periods of SLR were computed using ADCIRC storm surge model. The contribution of storm waves to the non-overtopping crest elevation was also studied using a nearshore wave model. Return periods of various design water levels were also associated with the various SLR and GCC scenarios to establish bases for the rehabilitation design of the RB seawall.