1983 scale mountain slide, Gansu Province, China

Unpublished reports of investigations carried out after the 1983 Sale Mountain landslide and some of the published papers related to the occurrence, mechanism, and mobility of the landslide are reviewed herein. The landslide occurred on the high, steep south slope of Sale Mountain, which comprises nearly horizontal Pliocene silt-stones and mudstones covered by 120 m of Pleistocene eolian loess. The volume of loess involved in the slide was less than one-third of the total volume of the sliding mass, so it is was not a loess landslide, but a loess-covered mudstone landslide. Although the landslide occurred suddenly, before its occurrence there was a long-term preparatory stage, in which gravitational creep and tension fracturing were important processes leading to the final abrupt failure of the slope. Most researchers have suggested that the mechanism of the landslide was progressive failure that began with extremely slow sliding and tension fracturing, and ended with shearing through resisting elements across the bedding of the Pliocene sediments. The sliding velocity of the landslide was extremely rapid. The average velocity was approximately 20 m/s. The Fahrboeschung is 11 degrees , which represents an excessive travel distance of 1120 m.