泥石流沟岸堆积体侧蚀破坏的随机性

The randomness of lateral erosion failure of debris flow gully deposits

山区小流域沟岸的崩滑堆积体是泥石流形成和补给的重要物质来源,且在震后,随着时间的推移,这种补给作用越来越重要。为了研究沟岸堆积体在径流作用下的侧蚀破坏过程和规律,利用室内水槽,开展了不同上游来流流量、底床坡度以及细颗粒含量的侧蚀破坏过程研究,重点对实验中堆积体侧蚀破坏的现象、过程和其中的随机性特征和规律进行分析总结。结果表明,在不同实验中,沟岸堆积体侧蚀破坏过程主要包括坡脚侵蚀阶段和失稳崩滑阶段,坡脚侵蚀阶段连续而稳定,动力条件主要为水力侵蚀;失稳崩滑阶段的主要动力为重力侵蚀,土体失稳活动在该阶段表现为间歇性和涨落性;土体失稳间歇时间和规模都可以视作随机序列,且失稳间歇时间服从Poisson分布,失稳规模服从Pareto分布。不同实验条件对土体失稳活动的影响主要体现在失稳间歇时间间隔即失稳频率的改变,土体失稳频率随着底床坡度和流量的增大而增大;在小坡度(3°)条件下,土体失稳频率随着细颗粒含量的增大而增大;随着底床坡度的增大(7°),失稳频率随着细颗粒含量的增多先增大后减小;在底床坡度较大时(11°),失稳频率随着细颗粒含量的增多而减小。研究结果可为泥石流的形成机理研究提供参考。

The collapsed and landslide deposits on the bank of the gully in mountain areas are significant material sources for the formation and supply of debris flow.After the earthquake,this replenishment role has been increasingly crucial over time.For studying the lateral erosion failure process and law of these accumulations under the action of flow in debris flow gully,the lateral erosion failure process of the deposits with different bed slope,upstream flow,and fine particle content was studied by laboratory flume experiment.This paper mainly analyzes and summarizes the phenomenon and randomness law in the process of lateral erosion failure of side-shore deposits in the experiments.The results show that the erosion process of the deposits mainly includes the erosion stage of slope toe and the instability stage.The slope toe erosion stage is continuous and stable,and the main dynamic condition is hydraulic erosion;the prime driving force in the instability stage is gravity erosion,and the soil failure in this stage shows paroxysmal and fluctuation.The interval time and the scale of soil failure can be regarded as random sequences,and the interval time fit Poisson distribution,and its magnitude fit Pareto distribution.The influence of different experimental conditions on soil failure activities is mainly reflected in the instability frequency.The frequency of soil failure increases with the increase of the slope gradient and flow.Under the small bed slope gradient(3°),the frequency of soil failure increases with the increase of fine particle content.With the increase of bed slope gradient(7°),the frequency of soil failure increases first and then decreases with the increase of fine particle content.When the bed surface is in a steeper slope condition(11°),the frequency of soil failure decreases with the increase of fine particle content.The research results can provide a reference for the analysis of the formation mechanism of debris flow.