Topography and volume effects on travel distance of surface failure.pdf

Topography and volume effects on travel distance of surface failure Yoichi Okura a,*, Hikaru Kitahara b,1, Akiko Kawanami c,2, Ushio Kurokawa a aForestry and Forest Products Research Institute, P.O. Box 16, Tsukuba Norin, Ibaraki 305-8687, Japan bShinsyu University, Nagano, Japan cForestry Agency, Tokyo, Japan Received 16 August 2001; accepted 7 June 2002 Abstract The authors investigated factors affecting the travel distance of a surface failure and developed a simple model for estimating the distance based on soil properties and topographic factor. The authors conducted field surveys and various soil tests for a number of surface failures that occurred during torrential rain at the end of August 1998 in southern Fukushima Prefecture, Japan. The authors studied the effects of various factors such as landslide volume, pore-water pressure, slope inclination, and the internal friction near the slip surfaces on the travel distances. The analyses showed no clear relationship between landslide volume and equivalent coefficient of friction, which was likely attributable to the very small range of volume compared to other studies on catastrophic landslides. The effect of excess pore-water pressure was likely negligible because undrained conditions were not to be maintained at the shallow flow depths. A positive correlation was shown between slope inclination and equivalent coefficient of friction. This correlation was attributable to two factors, one was positive correlation between the internal friction on the slip surface and slope inclination, and the other was the kinetic energy dissipation of moving mass that occurred at the inclination changing point between a slope and a sedimentary flat surface. The authors then developed a predictive model for critical flow inclination of landslide by installing the factors of soil properties and slope inclination factors. The model predicted equivalent coefficient of frictions, which were very similar to the observed values, thus