Preliminary Study on Loess Slumping Hazard between Northern Shaanxi and Western Shanxi along the Line of West-East Gas Transportation Project

P5; The loess slumping hazard is a special type of slope failures in the northern area of loess plateau of China. The characteristics of paroxysm and high frequency of the hazard always lead to ruin of cave-houses, as well as a high human casualties. The hazard is also seriously harmful to railways,highroads and long transporting pipelines. With the mechanisms of both landslide and falling, as well as the forming process of sliding followed by collapses, loess slumping is used to be treated as landslide or falling. Based on field investigations and lab analyses of the loess between Jingbian County of Shaanxi Province and Puxian County of Shanxi Province along the line of west-east gas transportation project which is 300 km long, it is discovered that the hazards of loess slumping are controlled by the content of clay, which lead to their obvious regional properties: the area with a content of clay (＜0. 005 mm) less than 10 %, called sand-loess area, is a seriously developing area of slumping; the area with a content of clay between 10 % and 20 %, called typical loess area, is a medium developing area of slumping; the area with a content of clay more than 20 %, called clay-loess area, is a non-developing area of slumping. Based on research of the formation mechanism and formation conditions of the loess slumping hazards, some corresponding engineering countermeasures are suggested in this paper.