地すべり面における地下水中の NaCl 濃度がスメクタイトに及ぼす影響

概要

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High concentration of Na^+, Ca^<2+> and Cl^- in ground water are important factors for the occurrence of landslide at Hanasaka in Komatsu City, Ishikawa Prefecture. Abundant Na^+ is always contained in ground water at the slip surface, while the amount of Ca^<2+> after the event has been reduced to one-thirty of that before the event. Smectite from the slip surface, the upper and the lower sediments has the peak at 13.8, 14.5 and 14.2Å respectively. The content of Na-smectite of the slip surface is more abundant than that of the upper and the lower sediments. The experiments on cation exchange of smectite in the solution which had the same concentration of Na^+ and Ca^<2+> as that in ground water at the slip surface shows the followings; partial Na-smectite with basal spacing of 12.5Å has exchanged an interlayer cation for Ca^<2+> (14.2Å ), and Ca-smectite (15.0Å ) has been shifted to 14.4Å. The result has revealed that dissolved ions of Na^+, Ca^<2+> and Cl^- in the solution affect swelling rate, cation exchange and water absorption of smectite. The factors in weakening the ground are considered to be (1) aggregation of the clay minerals, (2) remarkable swelling rate and water absorption of Na-smectite, (3) cation exchange of Na-smectite for Ca-smectite. leading to dehydration and contraction of Ca-smectite.
日本粘土学会の論文
1998-03-31