Wave trasformation on pebble beach and deformation of the beach

近年来，缓坡透水海堤代替陡坡混凝土海堤得到了广泛的应用。原因是前者具有有效的减少波浪上升和堤防反射的功能，并为在堤防上建立新的生态系统提供了空间。本文首次研究了用卵石筑成的透水缓坡海堤的水力功能。海堤的变形也在实验室和现场进行了检查。Deguchi和Sawaragi在二维波浪槽中进行了实验，研究了波浪在不同坡度和表面元素的模型海堤上的变换和上升。研究发现，波浪在透水斜坡上耗散能量，使波浪高度衰减，从而使破波深度和破波高度显著减小。随着坡面卵石粒径的增大和坡面坡度的减小，减小的速率也随之增大。特别是透水边坡上的波浪上升高度小于不透水边坡的一半。在此基础上，利用非线性非定常达里定律对渗流层流体运动进行求解，建立了预测渗流坡面波高和波高的数值模型。预测结果与实测的浪高和浪高相当吻合。Ono和Deguhi在实验室中研究了由鹅卵石制成的海堤的二维变形和位于大阪湾南部的用大理石鹅卵石建造的大理石海滩的三维地形变化。发现所谓的沉积型剖面变化是由陆上卵石净搬运引起的。在野外和实验中，卵石坡的平衡剖面与Dean的剖面相吻合。

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.