Tsuyoshi Ikeya

Tsunami Wave Force Acting on Axisymmetric Caisson Foundations

Tsunami wave force acting on the axisymmetric caisson foundations was investigated through the hydraulic model tests. Water surface profile of tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake observed 11m deep and 3km offshore of Choshi city (Fukumoto et al. , 2012) was used as the incident wave. By using the pumptype tsunami wave maker the observed tsunami profile was well reproduced in the wave-basin. Tsunami wave pressure distribution and wave forces acting on the axisymmetric caisson foundations were measured. Based on these experiment data, a mathematical formula expressing peak wave pressure distribution with the parameter of the incident tsunami height was proposed.

SLIT-TYPE WAVE ABSORBING STRUCTURE APPLIED ON STEEL PIPE SHEET-PILE CELLULAR SEAWALL

In the Tokyo International Airport (Haneda Airport) expansion project, the 13 runway will be constructed as a hybrid type structure with the piled-elevated platform and the reclaimed island. in the connecting area of the both part, a wave absorbing structure is planed to construct on the steel pipe sheet-pile cellular seawall to avoid the oecurrence of uplift pressure under the platform and the high reflection waves. The hydraulic model tests for the slit-type wave absorbing structures have been performed to measure the wave reflection ratio and wave pressure distribution on the structure. This experiment showed the most suitable settings of the wave absorbing structure for the project.

FUNDAMENTAL STUDY ON BEHAVIOR OF DRIFTING BODIES DUE TO TSUNAMI

The damage of the structures is classified into two types. The one is caused by the direct action of tsunami, and floating bodies such as destroyed facilities and drifting ships and cars cause the other one. The purpose of the present study is to investigate the damage on structures due to the drifting bodies with tsunami. In order to perform the investigation focused on a drifting body, experimental tests are carried out, and a combination method of non-linear long wave theory and DEM is suggested for drifting numerical models. The models are applied to reproduce the experimental tests. As a result, it is confirmed that suggesting method can predict the behavior of drifting bodies due to tsunami.

REDUCUTION OF WAVE FORCE ON A LONG CAISSON OF VERTICAL PLACED ON THE COMPLICATED SUBMARINE TOPOGRAPHY

As the length of a caisson becomes long, the wave force per unit length becomes smaller because of the wave phase difference. In this study, we performed hydraulic model test on a long caisson placed on the complicated submarine topography model under various wave conditions in order to investigate the characteristics of wave reduction.It is found that the wave force on a long caisson placed on the complicated submarine topography is reduced significantly in the case of oblique waves. The reduction ratio for multi-directional random waves is smaller than that for uni-directional random waves due to directional spreading. In the case of head-on waves, wave force per unit length on the long caisson becomes smaller because of the dispersion of the wave height and the phase due to wave refraction.

APPLICATIONS OF A NUMERICAL WAVE FLUME TO WAVE TRANSFORMATION ON A REEF

With rapid progress of computer technology, direct wave simulation techniques based on CFD (Computational Fluid Dynamics) have been applied to practical problems in coastal and/or port and harbor engineering. A numerical wave flume, which is considered one of the representative direct simulation techniques, has been expected to substitute for hydraulic model tests.In this paper, we consider characteristics of wave transformation on a reef, as one of the applications of the numerical wave flume to coastal structures. By observing its numerical results and comparing them with the experimental results previously obtained, we discuss its applicability to wave transformation on a reef.

SLIDING PHENOMENA OF THE CASISON BREAKWATER PLACED AT THE OFFSHORE EDGE OF BREAKER ZONE AND ANTI-SLIDING MEHTOD

The sliding of the caisson breakwater placed in the outer region of breaker zone with the sea bottom slope of 1:100 is studied. Through the hydraulic model tests, it is found out that when the law-frequency surface variation makes the water level law, the breaking wave impact pressure is appeared and makes the caisson slide. In order to increase the sliding resistance force and to reduce the sliding distance, the crushed stone back filling method is proposed. The validity of this method was verified through the hydraulic model tests and the numerical simulation based on the non-linear dynamic spring model.

UPLIFT PRESSURES ACTING ON LARGE PIER STRUCTURES BY MULTI-DIRECTIONAL RANDOM WAVES

Recently, plans of large pier structures, such as offshore airports and artificial islands, have been proposed. In order to design such structures safely and rationally, uplift pressures acting on them have to be precisely evaluated. The uplift pressures caused by regular waves have been studied and their behavior has been characterized by some researchers experimentally and theoretically.In this paper, the uplift pressures caused by multi-directional random waves are investigated through hydraulic model tests. The effect of taking the multi-directional random waves into consideration on the maximum values of impulsive wave pressures is discussed.