著者

船越 和也 上杉 大輔 江口 真由美 小川 恒一 水山 高久 黒川 興及 酒井 敦章

出版者

公益社団法人 砂防学会

雑誌

砂防学会誌 (ISSN:02868385)

巻号頁・発行日

vol.55, no.3, pp.43-49, 2002-09-15 (Released:2010-04-30)

参考文献数

9

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The influence of cement in concrete on water quality and fish was studied experimentally. In the summer of 2001, an accident occurred where fish died in a torrent. It was said that the accident was caused by fresh concrete used for sabo structures partly running out into the torrent. That kind of accident has, however, not been reported to date in the field of sabo works. Mortar test pieces were used to study the influence of cement on water and fish in the experiments. The mortar test pieces raised the pH of water up to 11.54 at maximum. When cement was mixed into water directly, the pH of the water went up rapidly even if the quantity of the mixed cement was little, resulting in damage to the Japanese goldfish used in the test. A number of Japanese goldfish died when the pH of water exceeded 10.80. Air entraining agents do not affect the pH of water. Since there is a fear of cement greatly affecting the quality of water and the lives of fish, when concreting sabo structures, it is necessary to take great care to avoid fresh concrete running into the water and increasing its pH to the point of killing fish.

著者

谷口 房一 小川 恒一 水山 高久 藤田 正治 小杉 賢一郎 扇 行徳

出版者

砂防学会

雑誌

砂防学会誌 : 新砂防 = Journal of the Japan Society of Erosion Control Engineering (ISSN:02868385)

巻号頁・発行日

vol.52, no.2, pp.27-30, 1999-07-15

参考文献数

4

被引用文献数

3

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Typhoon 7 hit Honshu on September 22, 1998. This storm brought about a certain amount of local damage in the path of the typhoon. Trees in the southern part of Nara Prefecture were blown down. Field survey and analysis of aerial photographs taken after the storm were carried out to determine some of the characeteristics of the trees blown down. Along narrow gorges the blown down trees on the steep slopes lay scattered in the direction of the downward grade. The blown down trees on slopes in the open areas lay in the same direction as the blast of the wind.The most trees blown down entirely from their roots and a few trees were broken at the middle of their trunks. The structure that check the outflow of the downed trees and the incidental landslides or debris flow sediment was proposed to be built from the logs of rather large diameters available at the sites.