分形特征下降雨诱发砂土泥石流启动机理

利用分形理论计算不同颗粒含量砂土的粒度分维值，开展降雨条件下砂土泥石流启动模型试验，分析试验现象、位移场及含水率变化情况，总结分形特征下泥石流的启动机理。研究结果表明：粒度分维值随细粒含量的增加而增大，坡体发生明显现象的时间越早，泥石流启动的总体历时越长。分维值较大时，以坡表侵蚀破坏为主，坡表整体位移均匀，启动历时长；雨水分布不均匀，滑动带内外含水率差异显著，持水时间长；分维值较小时，以滑坡型破坏为主，启动历时短，产生位移大；雨水运动以渗流为主，土体抗剪强度降低，滑动带内外含水率差异减小，持水时间逐渐消失。分维值大小适中时，以过渡型破坏为主，泥石流启动时位移最小，历时较长，灾害程度最轻。

A Study on Starting Mechanism of Sand Debris Flow of Rainfall Type with Fractal Characteristics

The granularity fractal dimensions of sand with different particle contents are calculated based on fractal theory. The starting model tests of sand debris flow under rainfall condition are carried out, in order to analyze the changes of testing phenomenon, displacement fields and water contents. The starting mechanism of debris flow with fractal characteristics are concluded. The study results show that, with the increaing fine grain contents, the granularity fractal dimensions is larger, the occurring time with obvious phenomenon on slope is earlier, and the starting duration of devris flow is longer. When the granularity fractal dimensions is relatively large, the erosion failure is mainly occurred on shallow slope. The overall displacement of shallow slope is relatively uniform. The starting duration is longer. The rainwater distribution is not uniform. The water contents in and out the sliding zones are significantly different. The water holding time is longer. When granularity fractal dimensions is small, sliding failure is mainly occurred. The starting duration is shorter, resulting in larger displacement. The rainwater transfer is mainly seepage flow. The shear strength of soil is decreased. The differences of water contents in and out the sliding zones are decreasing. The water holding time is gradually disappeared. When granularity fractal dimensions is moderate, transitional failure is mainly occurred. The displacement is the smallest when starting debris flow. The duration is relatively longer, and the disaster is the slightest.