海水飛沫帯における橋脚砂岩塊のくぼみ深さに関する定量的把握 : 日南海岸・青島弥生橋の事例

概要

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Tafoni-like depressions occur on sandstone blocks used for a masonry pier of Yayoi Bridge at Aoshima Island on the Nichinan coast. The blocks are exposed to the spray zone and suffer weathering and wave erosion. The depth of depression was measured for all blocks in 1971, 1989, and 2001 corresponding to 20, 38, and 50 years, respectively, since the construction of the bridge. Rock strength of sandstone blocks was measured using an Equotip hardness tester. These data showed that the depth of depressions was smaller in the blocks having larger strength. The depth was described as a function of the salt weathering susceptibility of sandstone blocks W_s, the height above mean high water level h^* located the blocks, and time t ; the depth D was expressed by : D=68.6W_se^<-0.0038h^*>(1-e^<-0.031t>) where W_s is represented by W_s=P/S_t, P is the total pressure potential generated in unit volume of the rock, and S_t is the tensile strength estimated from Equotip hardness.
日本地形学連合の論文
2005-01-25