Wave trasformation on pebble beach and deformation of the beach

近年来，以透水斜坡代替陡坡混凝土海堤的缓坡海堤得到了广泛的应用。这是因为前者能有效地减少波浪爬高和反射作用，为在堤上创造新的生态环境提供了空间。本研究首先探讨卵石筑成透水缓坡海堤之水力功能。此外，还在实验室和现场对海堤的变形进行了研究。出口和泽原木在二维波浪水槽中进行了实验，研究了不同坡度和表面要素的海堤模型上的波浪变形和爬高。结果表明，波浪在透水斜坡上耗散能量，波浪高度衰减，波浪破碎深度和破碎高度显著减小。随着坡上卵石粒径的增大和坡度的减小，减小速率增大。尤其是透水坡上的波浪爬高小于不透水坡上的一半。然后，他们建立了数值模型，预测波高和波浪爬高的渗透性斜坡上应用非线性不稳定的Dary定律的流体运动在透水层。Ono和Deguhi在实验室中研究了由卵石制成的海堤的二维变形，并在位于大坂湾南部的大理石卵石建造的大理石海滩中研究了三维地形变化。结果表明，卵石净向岸运移引起了沉积型剖面变化。卵石边坡的野外和试验平衡剖面均符合Dean剖面。

Recently gentle slope sea dikes with permeable slope instead of steep slope concrete dikes have been constructing widely. The reason is that the former have effective function to reduce wave run-up and reflection from the dike and give room for creating new ecosystem on them. In this study, hydraulic function of permeable gentle slope sea dikes constructed using pebble is first investigated. The deformation of the sea dike is also examined in the laboratory and in the field.Deguchi and Sawaragi carried out experiments in 2-D wave tanks to examine wave transformation, run-up on the model sea dikes of various slope and surface elements. It is found that waves dissipate their energy on the permeable slope and decay their height and consequently the depth of wave breaking and the wave breaking height decrease remarkably. The rate of decreases becomes large with the increase in the size of the pebble on the slope and with decrease in the slope. Especially, wave run-up height on the permeable slope is less than a half of the on the impermeable slope. Then they constructed numerical model for predicting wave height and wave run-up on the permeable slope by applying a non-linear unsteady Dary's law for the fluid motion in the permeable layr. The predicted results coincide fairly well with the measured wave height and run-up.Ono and Deguhi investigated 2-D deformation of the sea dikes made of pebble in the laboratory and 3-D topography change in the Marble Beach constructed using pebble of marble and locating on the southern part of Osaka Bay. It is found that a so-called depoitional type profile change took place by net onshore pebble transport. The both equilibrium profiles of the pebble slope in the field and experiments coincide with the Dean's profile.