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1.

論文(リポジトリ)

論文(リポジトリ)
古谷, 元 ; 末峯, 章 ; 丸井, 英明 ; 佐藤, 修 ; 原, 龍一 ; 岡本, 敦
出版情報: 新潟大学積雪地域災害研究センター研究年報 — 新潟大学積雪地域災害研究センター研究年報.  24  pp.19-25,  2002-12.  新潟大学積雪地域災害研究センター
本文リンク: http://hdl.handle.net/10191/39249
概要: We carried out investigation of soil temperature at one-meter depth and water quality (water temperature and electric conductivity) to make clear relationship between slope failure and groundwater flow at source area of debris flow in the Tobinosu-dani-A stream, Zentoku, Tokushima, Japan. Furthermore, we investigated water temperature and electric conductivity of springs, at Tobinosu-dani-C stream, boreholes and underflow at Z6 block of Zentoku landslide to grasp the origin of groundwater. The results of our investigations are as follow. The groundwater flows at the source area of Tobinosu-dani-A stream are under flow type, which is flowing from outside of basin. Direction of these flows are Northeast to Southwest, which may be controlled to relative high permeability structure in the bedrock. The slope failure at source area of debris flow in this stream is caused by underflow from North to South. 続きを見る
2.

論文(リポジトリ)

論文(リポジトリ)
古谷, 元 ; 末峯, 章 ; 小山内, 信智 ; 原, 龍一 ; 佐藤, 修 ; 小松原, 岳史
出版情報: 新潟大学積雪地域災害研究センター研究年報 — 新潟大学積雪地域災害研究センター研究年報.  23  pp.35-44,  2001-12.  新潟大学積雪地域災害研究センター
本文リンク: http://hdl.handle.net/10191/39231
概要: Many debris flows caused by heavy rainfall have occurred at mountains in crystalline schist area, Shikoku Island, Southwestern Japan. The typical movement form of debris flow caused by heavy rainfall in mountainous area is fluidizing of soil mass from source area of debris flow to down slope (Stream). The debris flow at Tobinosu-dani stream in Zentoku, Nishiiyayama village on 29 June 1999 is this type of movement form. Therefore, it is important to make clear about occurrence mechanism of slope failures at source area of debris flow. Then, we carried out investigations of soil temperature at one-meter depth, water temperature and electric conductivity of springs and boreholes at the source area in the Tobinosu-dani stream and the Zentoku landslide. The results of our investigations are as follow. 1) There are two types of groundwater flows at the source areas of debris flows in the Tobinosu-dani stream that cause slope failure. One type is underflow changed by groundwater flow in deep layers with low value of electric conductivity. The other type is fissure water like groundwater vein-streams from deep layer with one digit higher value of electric conductivity than the underflow. 2) It is presumed that different of value of electric conductivity between underflow and fissure water is based on the different storage time (groundwater pass). Depth of the fissure water supply, especially, is corresponding to the approximate depth of the sliding surface (or bed rock) in the Zentoku landslide. 続きを見る
3.

論文(リポジトリ)

論文(リポジトリ)
丸井, 英明 ; 渡部, 直喜 ; 佐藤, 一幸 ; 吉川, 正徳 ; 南雲, 政博 ; 外山, 裕一
出版情報: 新潟大学積雪地域災害研究センター研究年報 — 新潟大学積雪地域災害研究センター研究年報.  20  pp.1-9,  1999-03.  新潟大学積雪地域災害研究センター
本文リンク: http://hdl.handle.net/10191/39196
概要: In the previous paper the background and mechanism of the Gamahara Torrent debris flow of 6 December 1996 were reported on the basis of the results of various geotechnical investigations. This report deals with results of the geological survey in two bore holes just behind of the slope failure scar and observation results of the behavior of the groundwater in the same bore holes due to the continuous measurement of the water table. As a result of the initial field survey it was estimated that the debris flow was triggered by the slope failure which occurred at the geological formation border at an elevation of about 1,300m and further the soil layer above the formation border probably contained very much water due to antecedent rainfall before the occurrence of the slope failure. Two bore holes for surveying are dug just behind of the slope failure scar in order to clarify the geological formation structure and to grasp the behavior of the groundwater regulated by the geological formation border. It was confirmed that the geological formation structure of the target area is generally corresponding with the structure estimated from the in situ field survey in the slope failure scar. The upper soil layer, the formation of the quaternary volcanics, is classified into two layers namely the upper pyroclastic flow deposit layer and the lower andesite lava layer according to the observation results of the boring core from the two bore holes. The observation results of the water table in one of the bore holes showed that the water table has significantly risen up by snow melt and quickly dropped down in the middle of April 1998. 続きを見る
4.

論文(リポジトリ)

論文(リポジトリ)
丸井, 英明 ; 渡部, 直喜
出版情報: 新潟大学積雪地域災害研究センター研究年報 — 新潟大学積雪地域災害研究センター研究年報.  20  pp.10-24,  1999-03.  新潟大学積雪地域災害研究センター
本文リンク: http://hdl.handle.net/10191/39201
概要: The background and the process of the Hachimantai debris flows of 11 May 1997 are reported. At first a big landslide occurred in the upper slope of the Sumikawa hot spring. Clearly the landslide was triggered mainly by snow melt and additionally by 110mm rainfall. The total volume of the slid soil mass was estimated to be 594,000,000m^3. From the toe area of the landslide a soil mass of 116,000,000m^3 flowed downward several times as debris flows along the Sumikawa torrent. Chemical analysis of the water contained in the debris deposit in the landslide area should provide an effective measure of identifying the origin of the water. Chemical analysis results showed that the water in the debris deposit did not originate directly from rainfall and snow melt but came from stored groundwater. This report interprets also the physical and mechanical properties of the unstable debris deposits in the landslide area as a source material of the debris flows. Various geotechnical investigations were performed in order to analyze the mechanism and the process of the debris flows. The shear strength parameters of debris deposits in the upper part and the toe part of the landslide area were determined by using a ring shear apparatus. 続きを見る
5.

論文(リポジトリ)

論文(リポジトリ)
丸井, 英明 ; 渡部, 直喜 ; 佐藤, 修 ; 前川, 峰志
出版情報: 新潟大学積雪地域災害研究センター研究年報 — 新潟大学積雪地域災害研究センター研究年報.  19  pp.23-48,  1998-03.  新潟大学積雪地域災害研究センター
本文リンク: http://hdl.handle.net/10191/39182
概要: The background and mechanism of the Gamahara Torrent debris flow of 6 December, 1996 is reported. It is very unusual that the debris flow occurred at the beginning of December in terms of the necessary water supply. Clearly the debris flow was triggered by landslide which occurred at the geological formation boundary at an elevation of about 1,300m. The soil layer above the formation boundary probably contained very much water due to antecedent rainfall before the occurrence of the landslide. Chemical analysis of the water contained in the debris flow deposit should provide an effective measure of identifying the origin of this water. Chemical analysis results showed that the water in the debris flow deposit did not originate directly from rainfall and snow melt but came from stored groundwater. This report interprets also the physical and mechanical properties of the unstable debris deposits in the various areas of the Gamahara torrent basin. Various geotechnical investigations were performed in order to analyze the mechanism and the process of the debris flow. The shear strength parameters of debris flow deposits on the torrent floor in the lower part of the watershed and slope failure deposits in the landslide scar which triggered the debris flow were determined by using a ring shear apparatus. 続きを見る