土砂流下実験における間隙水圧の動的変化と流下土砂の運動特性 [in Japanese] Pore-pressure fluctuation and run-out characteristics of the granular mass flow [in Japanese]
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準実規模水路を用いた土砂流下実験を実施したところ, 勾配部を流下する砂供試体中では, 流下土砂高さの1.5倍程度の圧力水頭発生が確認された。桜島から採取した軽石 (ボラ) 試料は, 単位体積重量が小さいため, 過剰な間隙水圧の発生がなくとも長距離運動することが示された。最大到達距離ならびに堆積する土砂の集合の程度の両視点から土砂流下現象を考える必要性を示し, これを表現する指標として, 運動特性指数 (等価摩擦係数と重心間の等価摩擦係数の比) を提案した。
Changes in pore-pressure and normal flow height in the granular mass flow had been investigated on sand and pumiceous gravel samples by quasi-real scale model flume tests. The excessive pressure head was observed under the sand flow, which was about 1.5 times as much as normal flow height. In the case of pumiceous sample, no excessive pressure head was observed, however, it traveled longer than the sand sample. This was because pumiceous sample had very small unit weight and it must have almost floated in the water during the experiments. The series of this experiments revealed that the both views of maximum travel distance and the extent of congregation of soil deposits were of great importance. For the sake of expressing the granular flow phenomena from those viewpoints, the new parameter "run-out characteristics index (ƒ)" was proposed as the ratio of the equivalent coefficient of friction (tan φ<sub><i>a</i></sub>) to the equivalent coefficient of friction between gravity centres before and after failure (tan φ<sub><i>ag</i></sub>).
Landslides 43(5), 283-293, 2007-01-25
The Japan Landslide Society