山地における地すべりデブリ流堆積の特徴

Characteristics of landslide-debris flow accumulation in mountainous areas.

• Zhang Qing-Zhao
• Pan Qing
• Chen Ying
• Luo Ze-Jun
• Shi Zhen-Ming
• Zhou Yuan-Yuan

抄録

地すべりデブリ流は、山地で発生する突発的な地質災害であり、大規模・高速・広範囲の衝撃範囲を特徴とし、しばしば悲惨な事故を引き起こすことがある。本研究では、屋内スライディングシュート試験を用いて、地すべり-デブリ流の移動過程とその堆積パターンを、開始勾配と粒度分布を考慮して検討した。また，PFCを用いてモデル試験を再現し，地すべり-デブリ流の実態に即した数値モデルを構築した．その結果、地すべりデブリ流の移動中に粒子の衝突が発生し、最終的な堆積物では明らかな選別現象が発生することがわかった。堆積物の表層と表面には粗い粒子が分布し、裏層と底部には微粒子が分布している。堆積物の形態には、開始角度が一定の影響を与え、開始角度が大きいほど、堆積物は谷の対岸に近くなる。粒子勾配は堆積物の形態や分布にも大きな影響を与え、粗粒子の割合が増えると、微粒子の堆積物は後縁中央に向かって縮小し、堆積物の形状はより平坦で凹凸があり、堆積物は谷の対岸に近くなり、堆積物の形状の角度が大きく増加する。

Landslide-debris flow is a sudden geological hazard in mountain areas, which is characterized with large scale, fast speed and wide impact range, and often causes disastrous accidents. In this study, an indoor sliding chute test was used to study the movement process of the landslide-debris flow and its accumulation pattern in the valley, taking into account the initiated gradient and particle size distribution. Besides, the model test was reproduced by PFC and the numerical models were constructed to fit the actual situation of landslide-debris flow. The results show that the collision of particles occurs during the movement of landslide-debris flow, and obvious sorting phenomena occur in the final deposit. Coarse particles distribute in the front and surface of the deposit while fine particles distribute in the back and bottom. The initiated angle has a certain effect on the morphology of the deposit: larger initiated angle makes the deposit closer to the opposite bank of the valley. Particle gradation has a significant impact on the form and distribution of deposit as well, with the increase of the proportion of coarse particles, the deposit of fine particles shrinks to the center of the rear edge, the profile of the deposit is more flat and uneven, the deposit is closer to the opposite bank of the valley, and the angle of the deposit profile increases significantly.

© 2019 The Authors. Published by Elsevier Ltd.