Rainfall, landslide and debris flow intergrowth relationship in Jiangjia Ravine

Jiangjia Ravine is a world-famous debris flow valley in Dongchuan, Yunnan Province, China. Every year large numbers of landslides and collapses happened and caused enormous damages to people's properties and lives. With longtime observation and testing in Jiangjia Ravine we had found out one kind of special landslide which had the characteristics of landslide and collapse. Landslide and collapse supplied sufficient materials for debris flow. When a debris flow broke out, some kind of intergrowth existed among rainfall, landslide and debris flow. In order to study the intergrowth and some key parameters, we carried out artificial rainfall landslide tests and model experiments to observe the phenomena such as collapse, surface slide and surface flow. By observing the experimental phenomena and monitoring water contents, the transformation process among landslide deposits and debris flow under the condition of rainfall had been analyzed. Research results revealed the relationship of this kind of intergrowth among rainfall, landslide and debris flow in Jiangjia Ravine. Meanwhile, it was found that this kind of intergrowth relationship existed only when the moisture content was in a certain range. That is, the critical state seemed to be existed in the transformation process.