滑坡转化泥石流起动的人工降雨试验研究

ARTIFICIAL RAINFALL EXPERIMENTAL STUDY ON LANDSLIDE TRANSLATION TO DEBRIS FLOW

滑坡转化泥石流起动的人工降雨试验研究是把握滑坡转化泥石流过程和机制的重要研究手段。选择泥石流典型流域——云南蒋家沟上游泥石流形成源地的弯房子和下游泥石流堆积地的大凹子沟口分别进行野外人工降雨原型试验。通过对全流域泥石流形成背景的考察来确定典型坡度、土体特征和植被条件等因素,从而选定试验地点。共实施了8场野外人工降雨下滑坡转化泥石流起动试验。采用国内外较为先进的试验设备和观测手段,实时监测了试验过程中土体特征参数的变化,包括土体水势、体积含水量、孔隙水压力和温度等,并录相观测试验过程中发生的现象。通过初步分析发现,泥石流宽级配砾石土具有以下特征:(1)在强降雨下,滑坡转化泥石流的起动机制是振动软化或液化;(2)土体破坏时可能处于饱和状态,也可能处于非饱和状态,试验结果并不支持饱和液化机制;(3)在泥石流源地试验时,部分试验的水势曲线在下降过程中表现出短时间的剧烈波动现象,表明土体破坏过程中存在土体强度的降低和恢复的交替过程;(4)土体破坏过程中存在能量交换;(5)在强降雨下,滑坡启动与泥石流形成是一个连续过程,土体破坏过程中表现出了泥石流的特征。

It is important to grasp the process of landslide translation to debris flow on me oasis of me experiment of landslide translation to debris flow. Four artificial rainfall experiments have been carded out at Wanfangzi, located in the debris flow source area of Jiangjia Ravine, and other four experiments have been performed at the deposit area. The Jiangjia Ravine is a famous debris flow gully. After investigating whole drainage area, the conditions and locations of these experiments are determined. In the process of these experiments, some soil parameters have been measured through some advanced equipments. These parameters are water potential, water content, pore water pressure and soil temperature. After primary analysis have been completed, some basic characteristics of wide-graded gravel soil are presented. Main conclusions include： （1） under the strong-intense rainfall, the mechanism of landslide translation to debris flow is the vibration softening or the vibration liquefaction, and the soil strength can be expressed by the function of grain grade, saturation, and pore water pressure induced by the vibration and infiltration rate; （2） when soil is broken, the soil may be unsaturated, so the mechanism of saturation liquefaction has not been applied： （3） when the curve ot water potential oeclmes, me process of soil strength fluctuation will be validated; （4） the energy exchange exists in the process of soil break; and （5） under the strong-intensity rainfall, it is difficult to distinguish the start of landslide against the formation of debris flow, because the characteristics of debris flow appear when soil is broke.