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

从1999年开始，研究了海浪对滨海喷雾区石工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四个桥墩是金字塔形状的锥体。桥墩分别称为P1、P2、P3和P4。大多数砂岩块覆盖了桥墩的所有侧壁，表面有一块类似塔夫尼的凹陷。各壁的平均凹陷深度在P4时最大，P3、P2时逐渐减小，P1时最小。因此，通过测量波浪对砂岩块的海水补给量，以阐明海水喷雾在上述趋势形成中的作用。研究结果如下：1.在北向墙上，对砂岩块的海水补给量在P1处最大，然后逐渐减少到P4处。这表明平均凹陷深度与海水供给量成反比。在朝南的墙面上，海水供给量在P2上显示最大。这与P2.3喷雾区凹陷深度最小有关。由于在正常海况下，海浪从北面靠近，因此北面和南面墙的海水供给量有显著差异。此外，海水供应量的这种差异在P1.4上是最大的。P2各墙海水补给量北向墙最大，南向墙最小，东、西向墙最小，说明砂岩块的海水补给量在凹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.