Field tests of a sled system for beach profile measurement and of bed load sampler at T-shaped observation pier

利用京都大学电力研究所绪方波浪观测站的T形观测墩，对风暴波条件下的底地形和输沙率进行了现场测量。首先研制了一种带压力传感器的底剖面仪，然后根据采样器周围局部冲刷和孔口放水的思想，研制了一种推移质采样器。主要结论如下：1.即使在风浪条件下，使用TOP剖面仪也可以获得精确的三维海底地形。码头周围的海滩过程与绪方海岸相同。倾向和浅滩几乎是逐年稳定的，这一特征在冬季风暴波下很好地固定。此外，由于混凝土护面单元沿海岸线沿着排列，反射波产生的离岸泥沙输运导致浅水区泥沙流失和水深增加。特别是在桥墩离岸翼的伦敦东区，在涌浪条件下可以检测到强烈的底流。推移质采样器可以在半波周期内捕获输沙率。取样器下料斗部分周围的局部冲刷可将其固定在同一位置。在另一个半波周期内，通过入口距海底50cm手肘引入海水可以扩散.推移质输沙资料与作者从理论上推导的波浪输沙公式符合较好。

The in situ measurement of the bottom topography and the rate of sediment transport under storm wave conditions have been studied with T-shaped observation pier(TOP) at Ogata Wave Observatory, DPRI, Kyoto University. First of all, a bottom profiler equipped with a pressure sensor could be developed and secondly a bed load sampler was made on the basis of the ideas of local scour around the sampler and discharge of water from the opening. The principal conclusions are as follows:1. It is possible to get an accurate three dimensional bottom topotraphy with the profiler at TOP, even if under storm wave conditions.2. The beach processes around the pier is as same as those on the Ogata Coast. the dip and shoal are nearly stable year by year and this feature is well fixed under storm waves in winter. Moreover, the offshore sediment transport generated by the reflected waves due to concrete armor units lined up along the shoreline leads to loss of sediment in the shallow water area and increment of water depth. Especially, at the east end of the offshore wing of the pier, a strong undertow can be detected under swell wave conditions.3. The bed load sampler can trap the rate of sediment transport during a half wave period. The local scour around the lower hopper part of the sampler can fix it at the same position. The intake of sea water through the elbow pipe whose entrance is at the height of 50cm from the sea bottom can spread out during another half wave period.4. The data of bed load transport are fairly good agreement with the present formula of sediment transport by waves which is theoretically derived by the author.