A study on hydrokinetic mechanism of high-speed landslides

Abstract

A large high-speed landslide occurred in the Touzhai valley in Yunnan province of China on September 23, 1991. The slide mass, approximately 18 million meters cubed in volume, moved with an average velocity of 28 m/s. Eventually part of the slide mass plunged into the Pan-he river within 2-3 minutes. The slide mass moved about 3.65 km. Clastic basalt filled up the 40 m deep valley and formed the 250 m wide landslide deposits. Detailed investigation of the landslide showed that the slide could be divided into three related stages according to time and space. The stages were set-out, short-range and long-range. Each stage had different hydrokinetic phenomena and motion characteristics. The slide mass slid rapidly along the slip surface in the set-out stage, flew at a speed of over 54 m/s in the short-range stage and turned into the fragment flow in the long-range stage. This paper analyzed the mechanism of high-speed and long run out all over the course and came to several conclusions. Copyright ASCE 2006.