降雨作用下滑坡转化泥石流分析研究

Studied on landslide translating into debris-flow under rainfall

对降雨入渗条件下诱发北川县魏家沟泥石流起动的影响因素进行研究。在室内人工降雨试验模拟泥石流起动的基础上,得到魏家沟泥石流起动的临界雨强,并利用FLAC软件建立降雨在坡体中入渗分析的数值模拟模型,分析坡度、雨强、土性参数以及土体饱和度对坡体失稳的影响,坡体在降雨情况下塑性区的出现与延展及坡面拉应力区的发展情况。研究结果表明:降雨入渗后孔隙水压力的升高主要在坡脚附近,即距坡脚1/5的坡高范围内。坡脚处孔隙水压力最大,沿着坡面往上逐渐减小,且坡面较大水平位移也主要集中在1/5坡高范围内。因此,降雨入渗诱发泥石流的起动最先可能出现在坡脚附近,并随着坡度增加、雨强增大、土体饱和度增大,坡体稳定性降低至失稳,促进泥石流的起动。

The parameters affected unsteady of landslide and induced of debris-flow under rainfall in Weijia Gully in Beichuan,Sichuan province were analyzed.Several experiments on the initiation of debris flow under different slopes were carried out in a flume before.The critical rainfall strength exciting the initiation of debris flow in Weijia Gully was obtained.Based on which the numerical model for modeling unsteady of landslide and initiation of debris flow under rainfall was established using the software FLAC.The effects of the slope,rain strength,soil parameters and saturation were investigated.The initiation and expansion of the plastic zone,and the development of the tensile stress zone in the slope under rainfall were also investigated.It indicated that the zone with high pore water pressure mainly near the slope toe with one fifth of the slope height.The pore water pressure at the slope toe was the highest,and decreased from the toe to top.The large horizontal displacements of the slope were mainly near the slope toe with one fifth of the slope height.Therefore,the initiation of debris flow under rainfall was first at the slope toe.With the increase of the slope angle and rain strength and saturation degree,the stability of the slope decreased to cause the debris-flow.