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論文(リポジトリ)

論文(リポジトリ)
児玉, 貴幸 ; 渡部, 直喜 ; 丸井, 英明
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.  22  pp.17-30,  2000-03.  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/10191/39226
概要: Landslides show intermittent activities in a long period. Such repeat of slip and stop might depend on the changes of shear resistance of the slip surface of landslides during chemical weathering. Several non-weathered and weathered mudstone samples were collected from same outcrops in the landslide area. Simple shear tests were carried out on these samples that were powdered and regulated on grain size and on water/rock weight ratio (W/R). Weathered mudstone samples having W/R>0.3 exhibited higher shear strength than non-weathered mudstone samples. Clay-mineral assemblage and chemical composition of these samples were determined by XRD method and XRF analysis, respectively. Clay-mineral assemblage and chemical composition of smectite in weathered mudstone samples are different from those in non-weathered mudstone samples. This suggests that clay-mineral assemblage and chemical composition of smectite influence to the shear strength of mudstones. Landslide activities are probably controlled by the changes of clay-mineral assemblage and chemical composition of smectite in the sheared mudstones formed by landslides during chemical weathering under the groundwater table. 続きを見る
2.

論文(リポジトリ)

論文(リポジトリ)
柚原, 雅樹 ; 相楽, 渉 ; 高橋, 俊郎 ; 渡部, 直喜 ; 山岸, 宏光 ; 丸井, 英明
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.  21  pp.73-82,  2000-03.  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/10191/39213
概要: The^<87>Sr/^<86>Sr and ^<143>Nd/^<144>Nd ratios, Rb, Sr, Sm and Nd concentrations were determined in surface waters and rocks collected from the Hieda-yama landslide area, Nagano Prefecture. The change of trace element concentrations, ^<87>Rb/^<86>Sr and ^<147>Sm/^<144>Nd ratios in andesite by chemical weathering supports dissolution of plagioclase by this process as indicated in Sagara et al. (1997). The ^<87>Sr/^<86>Sr and ^<143>Nd/^<144>Nd ratios, however, are almost constant, because Sr and Nd isotopic ratios among minerals have small variation. This is caused by its young formation age. The ^<87>Sr/^<86>Sr and ^<143>Nd/^<144>Nd ratios of surface waters in the Kanayama-sawa river are close to those ratios of andesites. However, ^<87>Rb/^<86>Sr and ^<147>Sm/^<144>Nd ratios are lower than the ratios of andesites. These observations indicate that Sr and Nd in surface waters originated from plagioclases of these andesites. 続きを見る
3.

論文(リポジトリ)

論文(リポジトリ)
相楽, 渉 ; 渡部, 直喜 ; 佐藤, 修 ; 丸井, 英明 ; 垣原, 康之
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.83-96,  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/10191/39178
概要: The Hieda-yama landslide area is located in the northwestern part of Nagano Prefecture. Landslides and debris flows have repeatedly occurred in this area. Bed-rock geology of this area is mainly composed of the Quaternary andesitic rocks. These andesites were weakly altered along joints and cracks in the rocks and are bearing secondary minerals such as pyrite, quartz and smectites. Ca and SO_4 ions of stream water are very concentrated in this landslide area. This fact suggests that the chemical weathering of andesitic materials is very active and the most important factor for occurrences of landslides and production of debris and soils. The chemical weathering in this area is dominated by the oxidation of pyrite, one of the secondary minerals by hydrothermal alteration. Rock forming minerals, particularly plagioclase are dissolved and their components are leached out by sulfuric acid formed by oxidation of pyrite. The annual rate of soil production by chemical weathering is estimated by using parameters such as average annual precipitation, catchment area, Ca concentration of stream water, density of soil and fresh andesite, and CaO content of fresh and weathered andesites. 続きを見る