地すべり発生後11年を経過している平山地すべりは, 現在でも一定以上の降雨量によって再滑動を繰返している。再滑動は, すべり面に作用すそ静的間げき水圧u_iが0.8kg/cm²以上のときに発生し, 滑動開始直後, u_w≧0.65P_eの動的間げぎ水圧が擦過粘土内に発生して, 短時間内に消滅することが判明した。また滑動後には陥没帯からの主働土圧が移動に影響するが, 主働土圧も降雨量に関係して増減するといった再滑動機構をもっている。したがって本地すべりの防止対策としては, 排水を強化し, 降雨時の静的間げぎ水圧発生を極力抑えると同時に, 陥没帯の主働土圧に対しても考慮を払う必要がある。

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On April 26 pm 3 o'clock 1974, in Akamatsu district, Okuramura, Mogamigun, Yamagata Prefecture, occured the large scale landslide (90-160m wide, 415m long) with large amount of debrisslide. The main part of village was buried under this debrisslide and then there occured heavy damage of 17 casulties and 20 razed houses.
In this area, lignite bearing sequence, which is constructed with soft lithic characters in general and contains large amount of water, is developed. In 1974, heavy snowfall (once a 20 years) attacked the proper area, and during several days before April 26 when the landslide occured, high temperature continued and caused the melting of the snowsis equivarent to the rainfall of 40mm/D.
This landslide is not caused by the breaking of the old pits, but by the superfluous humidities of upper horizone of the lignite beds. It is, so to speak, the surface landslide.

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The water quality was surveyed in the 4 landslide areas in Niigata prefecture for the purpose of the research of underground water. The 5 elements, which were HCO₃^-, Cl^-, SO₄^-- Ca⁺⁺+Mg⁺⁺ and Na⁺, were analyzed in the method of component analysis. In the result, the contribution of information is 87.3% with the first and the second principal axes. Drawn on the orthogonal plane with the principal axes, the sample points are classified into 3 groups. Mean while, the data which were sampled in 3 times on the same station make an triangle. The shapes of triangles are distinguished into 3 patterns.

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爆圧工法とは地すべり地などの粘性土を対象にダイナマイト爆圧を応用すれば, 爆圧時における高圧・高温による周面土の拡孔ならびに固化作用を生じることに着目して, すべり面を縫合するジベル式の抵抗体を数多く施工する埋設抵抗帯の造成を目的とした一種の抑止工である。

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