Discrete element analysis on influencing factors of deposit morphology of landslide dam
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摘要: 滑坡是形成堰塞坝的最主要原因,在地震、降雨、冰雪融水等作用下均可形成滑坡堰塞坝,而滑坡堰塞坝的堆积形态、范围等对评价堰塞坝的稳定性有着重要的影响。通过离散元方法(DEM),系统分析了三维条件下滑动距离、滑面出口宽度、滑面倾角、河床倾角、河谷形状对堰塞坝堆积形态的影响。研究结果表明:滑动距离和出口宽度对坝体高度影响最大;随出口宽度和坡面倾角的增加,坝长和坝宽分别呈线性增大和减小趋势;滑动距离可以有效控制滑体速度,进而影响堆积角大小;河床倾角主要影响坝长;对坝高、坝长、上下游绝对倾角正切值和堆积角正切值进行回归分析表明,数学模型契合程度高,说明其形态可以预测;引入2个参数λ和χ,对堰塞坝堆积特征进行了描述;河谷形状的影响主要体现在随着河谷底部宽度的增大,滑体爬高爬坡能力增强。研究成果对根据实际地形预测滑坡堰塞坝堆积形态进而评估坝体的安全性具有重要意义,可以为进一步开展堰塞湖溃决研究提供一定的参考。Abstract: Landslides are the most important reason of landslide dams and can be formed under the action of earthquakes, rainfall, ice and snow melting water. The deposit shape range of a landslide dam has an important influence on the stability evaluation. In this paper, the effects of sliding distance, sliding surface outlet width, sliding surface angle, riverbed inclination angle and valley shape on the deposit shape of landslide dams are analysed systematically by the discrete element method (DEM). The results are as follows: The sliding distance and outlet width have the greatest influence on the dam height. With increasing outlet width and sliding surface angle, the dam length and width linearly increase and decrease, respectively. Sliding distance can effectively control the velocity of the sliding body and then affect the forward dip angle. The angle of the riverbed mainly affects the length of the dam. The regression analysis of dam height, dam length, upstream and downstream absolute dip tangents and deposit angle tangent shows that the mathematical model fits well, indicating that its shape can be predicted. Two parameters, λ and χ are proposed to describe the deposit characteristics of the landslide dam. The influence of the river valley shape is mainly reflected in the fact that the climbing ability of the sliding body increases with increasing bottom width of the river valley. This study is of great significance for predicting the deposit shape of landslide dams and then evaluating safety and provides a reference for further research on the collapse of landslide lakes.
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Key words:
- landslide dam /
- deposit morphology /
- sliding distance /
- outlet width /
- riverbed angle /
- sliding surface angle /
- regression analysis
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表 1 试验方案
Table 1. Experimental schemes
组别 编号 滑动距离L/m 出口宽度a/m 坡面倾角η/(°) 河床倾角θ/(°) 河谷形状 A 1 2 1.0 30 0 “V”形 2 3 1.0 30 0 “V”形 3 4 1.0 30 0 “V”形 B 4 2 0.8 30 0 “V”形 2 1.0 30 0 “V”形 5 2 1.2 30 0 “V”形 C 2 1.0 30 0 “V”形 6 2 1.0 45 0 “V”形 7 2 1.0 60 0 “V”形 D 8 2 1.0 30 4 “V”形 9 2 1.0 30 8 “V”形 10 2 1.0 30 12 “V”形 E 2 1.0 30 0 “V”形 2 1.0 30 0 “U”形 2 1.0 30 0 “T”形 表 2 细观参数统计
Table 2. Statistics list of microscopic parameters
最小颗粒半径/cm 1.0 摩擦系数 0.4 颗粒粒径比 1.66 阻抗摩擦系数 0.6 颗粒密度/(kg·m-3) 2 650 法向阻尼 0.2 孔隙率 0.5 切向阻尼 0.2 接触法向刚度/MPa 50 接触切向刚度/MPa 50 表 3 参数指标统计表
Table 3. Statistics list of parameter indexes
编号 1 2 3 4 5 6 7 8 9 10 L′d/m 0.91 0.92 0.97 0.82 1.02 0.98 1.13 1.01 1.20 1.29 Ld/m 0.65 0.65 0.70 0.57 0.76 0.78 0.98 0.75 0.97 1.13 Lb/m 1.86 1.82 1.89 1.66 1.97 1.94 2.25 1.95 2.01 2.04 α′/(°) 19.43 17.78 18.12 21.36 16.65 16.30 12.54 21.33 23.58 24.02 β′/(°) 19.29 16.91 17.69 21.29 14.98 16.58 13.86 15.42 11.91 10.47 λ 0.35 0.36 0.37 0.34 0.39 0.40 0.44 0.38 0.48 0.55 ψ 0.65 0.58 0.60 0.71 0.53 0.55 0.44 0.61 0.59 0.57 -
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