Effects of Geomorphological Settings on Salt Weathering of Sandstone in the Coastal Spray Zone

自1999年以来，研究了波浪对海岸喷淋区砌体桥墩砂岩块体盐风化的影响。连接日本青岛岛和九州岛的弥生大桥的4个桥墩是金字塔形状的截锥体。桥墩分别称为P1、P2、P3和P4。大部分覆盖着桥墩所有侧壁的砂岩块，其表面都有一个类似塔福尼的凹陷。各壁平均凹陷深度在P4上最大，在P3和P2依次变小，然后在P1上最小。因此，测量了海浪向砂岩块提供的海水量，以阐明海浪在上述趋势形成中的作用。所得结果总结如下：1。在北向岩壁上，砂岩块体的海水供水量在P1处最大，向P4处逐渐减小。这表明平均凹陷深度与海水供水量成反比。在朝南的墙壁上，P2的海水供应量最大。这与P2.3上喷淋区凹陷深度最小有关。由于在正常海况下，波浪从北方来袭，因此在朝北和朝南的墙壁上，海水供应量有显著差异。这种海水供给量的差异在P1.4上最大。P2各墙的海水供给量北侧最大，南侧减少，东侧和西侧最小。这些结果表明，海水对砂岩块体的供应在坳陷的形成中起着重要作用。

The effects of waves on salt weathering of sandstone blocks used for a masonry bridge piers in the coastal spray zone has been studied since 1999. Four piers of Yayoi Bridge, connecting Aoshima island with Kyusyu island in Japan, are the frustum of a pyramid in shape. The piers are called as P1, P2, P3 and P4 respectively. Most of the sandstone blocks, which cover all side walls of the piers, have a tafoni-like depression on their surface. The average depression depth of each wall is the largest on P4 and gradually becomes smaller on P3 and P2 in due order, then the smallest on P1. Therefore, the amount of sea water supply to sandstone blocks by waves has been measured in order to elucidate the role of sea spray in the formation of the tendency mentioned above.Results obtained are summarized as follows;1. On the north-facing walls, the amount of sea water supply to sandstone blocks shows the largest on P1, then gradually decreases toward P4. This indicates that the average depression depth are inversely proportional to the amount of sea water supply.2. On the south-facing walls, the amount of sea water supply shows the largest on P2. This is related to the fact that the depression depth in the spray zone is the smallest on P2.3. Because waves approach from the north under normal sea conditions, the amount of sea water supply shows notable difference between north and south-facing walls. Also this difference in the amount of sea water supply is the largest on P1.4. The amount of sea water supply on each wall of P2 is the largest on the north-facing wall and decreases on the south-facing wall, then becomes the smallest on the east and west-facing walls.These results suggest that the sea water supply to sandstone blocks plays an important role in the formation of depressions.