Tsunami Wave Pressure Research Articles

Validation of tsunami numerical simulation models for an idealized coastal industrial site

ABSTRACT Numerous tsunami numerical models have been proposed, but their prediction accuracies have not been directly compared. For quantifying the modeling uncertainties, the authors statistically analyzed the prediction results submitted by participants in the tsunami blind contest held at the 17th World Conference on Earthquake Engineering. The reproducibility of offshore water level generated due to the tsunami with soliton fission significantly decreased when the nonlinear shallow water equation models (NSWE) was used compared to three-dimensional (3D) models. The inundation depth was reproduced well in 3D models. However, the reproducibility of wave forces acting on the structure and velocities over land was lower in 3D models than that in NSWE models. For cases where the impulsive tsunami wave pressure generated could not be calculated based on the hydrostatic assumption, the prediction accuracy of the NSWE models was higher than that of the 3D models. The prediction accuracies of both models were not improved at small grid-cell sizes. The NSWE model cannot simulate the short-wave component and vertical pressure distribution. Therefore, further developments in 3D models and smoothed particle hydrodynamics methods (SPH) are needed. The presented results contribute to the future development of tsunami numerical simulation tools.

Blind-Test Numerical Simulation of Tsunami Wave Pressure Acting on a Land Structure

The prediction performance of numerical models of tsunami wave pressure on land structures was investigated using blind tests. Two types of numerical models were used, based on the volume-of-fluid (VOF) method. Both models reproduced the experimental results well for water-level time series. For wave-pressure time series, some differences were observed between the two models in the vertical distribution of wave pressure during the initial rise. In both models, however, the experimental results showed that overall trends for total wave force were in good agreement. The experimental results produced a value slightly higher than the maximum wave force, suggesting that caution is needed when designing structures to ensure that wave force is not underestimated.

PHYSICAL MODEL OF TSUNAMI-LOADS ON A SEASIDE BUILDING ARRAY

The devastating damage to buildings and infrastructure caused by the 2011 Tohoku-oki earthquake and tsunami highlighted the importance of evaluating tsunami impacts in areas at risk of tsunami inundation for disaster prevention and mitigation. Evaluation technologies have been vigorously researched and developed over the past decade. A wide variety of numerical models exist that can potentially be applied to evaluate tsunami impacts. Furthermore, several either theoretical or empirical models to evaluate tsunami impacts, such as evaluation models of debris impact force and tsunami wave pressure, have been proposed. To validate these numerical and evaluation models, both experimental and theoretical benchmark tests have been conducted (e.g., Horrillo et al., 2015). Most of these tests have been conducted to validate models of tsunami generation, propagation, and inundation. However, the number of benchmark tests to validate tsunami loads are limited, and especially, those for complex terrains are rare. In this study, as a benchmark test to validate modeling of tsunami inundation and wave pressure, hydraulic experiments of tsunami inundations were conducted over a seaside area model, in which building arrays were installed. The inundation depth, velocity, and pressure were numerically predicted for the condition of the benchmark test, and then compared with the measured data for validation.

An Application of Semi-empirical Physical Model of Tsunami-Bore Pressure on Buildings

Characteristic patterns of tsunami wave pressure on buildings is divided into three types, depending on its vertical profiles and time, which is observed after the tsunami impacted the buildings. The first one is the impulsive pressure, which is observed just after the tsunami impacted the buildings. The second one is the bore pressure, which is observed after the impulsive pressures. The third one is the quasi-steady pressure, which is observed after the bores go away from the buildings. In this study, based on characteristics of bore pressure observed in a hydraulic experiment, a semi-empirical physical model of bore pressure is developed by applying a turbulent bore theory. Also, we present an application method of the semi-empirical physical model to evaluations of bore pressure with usage of numerical results of inundation simulations of two-dimensional nonlinear shallow water equation models. Furthermore, we apply the semi-empirical physical model to evaluations of pressure acting on buildings in an inundation area by carrying out numerical simulations of tsunami inundation.

RESPONSES OF CONCRETE VERTICAL WALLS TO TSUNAMI WAVE PRESSURES AND DEBRIS IMPACT

By carrying out a set of experiments on the responses of vertical concrete/RC walls to tsunami impacts, the characteristics of the responses of concrete/RC walls to tsunami impacts were investigated. Experiments on both the responses of walls to only tsunami wave pressure and those to both tsunami wave pressure and debris collision were carried out. In experiments on the responses only to tsunami wave pressure, flexural failure at the base of the wall was observed when the bending moment at the base of the wall was greater than the predicted cracking moment. In experiments on the responses to both tsunami wave pressure and debris impact, flexural cracks and failure at the base of the wall were observed in some cases, and impulsive oscillations whose frequency immediately after debris collision depended on the debris material were observed.

NUMERICAL AND HYDRAULIC EXPERIMENTS ON BORE PRESSURE DUE TO TSUNAMI

The 2011 Tohoku earthquake tsunami struck a wide area of the northeastern coast of Japan, and many coastal structures and buildings were damaged by the tsunami. Most of the buildings were damaged by the tsunami wave pressure. After the tsunami, characteristics of tsunami waive pressures have been investigated by many researcher, and are being clarified. As shown in previous studies, there are three regimes charactering the vertical pressure profiles. The first one is the impulsive pressure, which is observed just after the tsunami-bore impacted structures. In this regime, strong hydrodynamic pressures are generated by the fluid-solid impact process. After that, the bore pressure is observed, and both the hydrodynamic and hydrostatic pressures contribute the pressure profile. After that, the flow near the structures reaches a quasi-steady state, and the pressure profile becomes hydrostatic. Most of the evaluation equations of tsunami wave pressure proposed by the previous studies can be used against the impulsive pressures and the pressures in the quasi-steady-state regime. On the other hand, the characteristics and quantitative evaluations of the bore pressure remain immature. In this study, in order to clarify the characteristics of the bore pressure, experiments on the bore pressure are carried out, and furthermore, three-dimensional numerical simulations are also carried out.

Hydraulic experiments on tsunami wave pressure and their applications

原子力発電所の耐津波性能の向上に寄与する防潮堤や水密工の設計等においては，主要な外力である津波波圧・波力を適切に評価することが肝要である。本シリーズでは，津波波圧・波力に関する水理実験について2回に分けて解説する。第1回では，この種の実験に関する基礎的内容を紹介した。第2回では，原子力発電所の敷地内に設置された防潮堤，タンク，配管に作用する津波波圧・波力に関する実務的評価を念頭に実施された水理実験について解説する。

Development of Estimation Method of Tsunami Wave Pressure Exerting on Land Structure Using Depth-Integrated Flow Model

To design and construct land structures which can withstand earthquake-induced tsunami, it is most essential to evaluate tsunami wave force exerting on the structures quantitatively. This study, therefore, proposes the estimation method of tsunami wave pressure acting on a land structure using inundation depth and horizontal velocity at the front of the structure, which were calculated by a two-dimensional depth-integrated flow model. The comparison between the numerical and experimental results revealed that the proposed method could reasonably reproduce the vertical distribution of the maximum tsunami wave pressure exerting on a land structure.

Hydraulic experiments on tsunami wave pressure and their applications

Hydraulic experiments on tsunami wave pressure and their applications

2011年東北地方太平洋沖地震の津波シミュレーション解析：津波波源モデルの違いによる福島第一原子力発電所・福島第二原子力発電所施設周辺に作用する津波波力の差異の評価

Since the 2011 Tohoku-Oki Earthquake, evaluations based on a tsunami simulation approach have had a very important role in promoting tsunami disaster prevention measures in the case of mega-thrust earthquakes. When considering tsunami disaster prevention measures based on the knowledge obtained from tsunami simulations, it is important to carefully examine the type of tsunami source model. In current tsunami simulations, there are various ways to set the tsunami source model, and a considerable difference in tsunami behavior can be expected among the tsunami source models. In this study, we carry out a tsunami simulation of the 2011 Tohoku-Oki Earthquake around Fukushima Daiichi (I) Nuclear Power Plant and Fukushima Daini (II) Nuclear Power Plant in Fukushima Prefecture, Japan, using several tsunami source models, and evaluate the difference in the tsunami behavior in the tsunami inundation process. The results show that for an incoming tsunami inundating an inland region, there are considerable relative differences in the maximum tsunami height and wave pressure. This suggests that there could be false information used in promoting tsunami disaster prevention measures in the case of mega-thrust earthquakes, depending on the tsunami source model.

Evaluation of Tsunami Wave Loads Acting on Walls of Confined-Masonry-Brick and Concrete-Block Houses

Damage to confined-masonry-brick or concrete-block house was assessed for being subjected to a tsunami wave load. This study was prompted by recent three tsunamis – one during 2001 on the Near Coast of Peru, one in 2009 in the Samoa Islands, and one in 2010 in Maule, Chile. We analyzed 13 damaged walls from 10 single-storey houses located near the coastline. We focused on evaluating the tsunami wave pressure distribution on house walls. Based on the formula proposed by Asakura et al. (2000) to evaluate tsunami wave pressure distribution on a structural component located on land behind on-shore structures, which is used for designing a tsunami evacuation building, we identify the values of horizontal wave pressure indexain Asakura’s formula for walls and discuss the boundary value ofaat which a wall presents structural damage, such as in collapse and cracking failure modes.

Stability of non-vertical waterfront retaining wall supporting inclined backfill under earthquake and tsunami

The stability analysis has been carried out for generalized non-vertical waterfront retaining wall supporting inclined backfill under combined action of earthquake and tsunami forces. Closed-form design solutions for factor of safety against sliding have been obtained using limit equilibrium method. For estimating seismic passive earth pressure and the wall inertia force, the pseudo-dynamic approach has been adopted. Different methods available in literature are used to estimate tsunami wave pressure and hydrodynamic pressure. It has been observed that parameters like seismic accelerations in both horizontal and vertical directions, time period, soil and wall friction angles, wall batter, ground inclination, pore pressure ratio, tsunami wave height have significant effect on the sliding stability of the waterfront retaining wall under combined action of earthquake and tsunami. Comparison of results with available results in literature for special case of vertical waterfront retaining wall supporting horizontal backfill has indicated a very good agreement. It is expected that the proposed design charts and tables presented in this paper will be helpful for the design engineers to design waterfront retaining wall against sliding mode of failure under combined action of earthquake and tsunami.

陸上構造物に作用する津波波圧と波向の影響に関する実験的研究

Hydraulic experiments to inspect the influence between tsunami wave direction and wave pressure acting on shore structures has been conducted. Cubic and cylindrical foam structures on which pressure gages are attached are installed in the wave basin and are able to rotate themselves to measure tsunami wave pressure with some incident angles. Surge tsunamis are generated under the condition with various still water depths and wave heights including impulsive undular bore. Observed wave pressures on the structures tend to decrease with the increase of the incident angle of the tsunamis. Additionally, 3D numerical simulations to reproduce the experiments have been done, which well agreed with the experiments if the wave direction is not greater than 45 degree and large impulsive wave pressure is observed.

開口影響を考慮した陸上構造物に作用する津波持続荷重の評価方法

開口影響を考慮した陸上構造物に作用する津波持続荷重の評価方法

初期浸水を有する陸地へ遡上した津波による構造物への作用波圧

初期浸水を有する陸地へ遡上した津波による構造物への作用波圧

構造物前面の流体現象に着目した津波波圧の特性

構造物前面の流体現象に着目した津波波圧の特性

構造物前面の水理量を用いた津波波圧算定方法の構造物群への適用性

Hydraulic experiments on tsunami wave pressure were conducted in the presence of multiple rectangular structures. A 2D depth-integrated flow simulation based on the unstructured grid system was carried out to reproduce run-up tsunami deformation. Tsunami wave pressure was calculated by using inundation depth and horizontal velocity at the front of the land structure. Even though splash due to the initial impact of the leading edge on the structure cannot be reproduced by the 2D simulation, the evaluation method of tsunami wave pressure could reasonably estimate the vertical distribution of the maximum tsunami pressure. Tsunami wave pressures calculated by CADMAS-SURF/3D were in good agreement with the experimental results on the condition that the evaluation method using the 2D simulation results cannot replicate.

陸上構造物に作用する津波持続波圧に関する水理学的考察

Hydraulic mechanism of sustained tsunami wave pressure acting on land structures was investigated theoretically. The effect of wave pressure amplification due to wave reflection was estimated based on momentum conservation law. On the other hand, backwater effect was modeled by energy conservation law. The formulas which indicate wave pressure on 2D wall and 3D structure were derived. The theoretical result was compared with the hydraulic model test results and numerical computation results and good agreement was found out.

Applicability of CADMAS-SURF to evaluate detached breakwater effects on solitary tsunami wave reduction

Detached breakwaters, made with wave-dissipating concrete blocks such as Tetrapods, have been widely applied in Japan, but the effectiveness of such kinds of detached breakwaters on tsunami disaster prevention has never been discussed in detail. A numerical wave flume called CADMAS-SURF has been developed for advanced maritime structure design. CADMAS-SURF has been applied mainly to ordinary wave conditions such as wind waves, and little attempt has been made for expanding its application to tsunami waves. In this study, the applicability of CADMAS-SURF for evaluating the effectiveness of detached breakwaters on a solitary tsunami wave reduction is investigated by comparing the calculated results with those from hydraulic experiments. First, the effectiveness of a detached breakwater on the reduction of wave height and wave pressure was confirmed both by hydraulic experiments and numerical simulations. Finally, CADMAS-SURF has been found to be a useful tool for evaluating the effects of detached breakwaters on tsunami wave height and pressure reduction, as a first step in a challenging study.

構造物前面の浸水深と流速を用いた津波波圧の評価手法に関する水理実験

Hydraulic experiments were conducted to estimate tsunami wave pressure acting on several different types of land structures and examine the influence of a seawall in front of the structure on tsunami wave pressure. Wave pressures were measured at some points on the structure. The existing hydrostatic formula tended to underestimate tsunami wave pressure under the condition of inundation flow with large Froude number. Estimation method of tsunami wave pressure using inundation depth and horizontal velocity at the front of the structure was proposed based on the experimental results. It was confirmed from comparison with the experiments that the vertical distribution of the maximum tsunami wave pressure can be reproduced by employing the proposed method in this study.