PRELIMINARY STUDY ON LOESS SLUMPING IN THE AREA BETWEEN NORTHERN SHAANXI AND WESTERN SHANXI──TAKING THE PIPELINE FOR TRANSPORTING GAS FROM WEST TO EAST IN CHINA

The hazard of loess slumping is a special type of slope failure in the northern part of China loess plateau. The paroxysm and high frequency of the slumping always lead to cave-houses and general houses to collapse, people casualties, and seriously damage of railways, highways and long pipelines. The loess slumping is of two mechanisms, landslide and collapse, and a deformation process of sliding followed by collapse. So it was usually treated as landslide or collapse. Based on field investigation and microscopic analysis of the geologic hazard of loess in an area 300km between Jingbian county of Shaanxi Province and Pucian County of Shanxi Province, the authors found that the hazards of loess slumping are controlled by the content of clay, which has obvious regional character: the area with content of clay (0.005m) less than 10%, is called sand-loess area, in which of slumping is most heavy. The area with content of clay between 10% and 20% is called typical loess area in which slumping is weak. The area with content of clay more than 20% is called clay-loess area in which no slumping is developed. On the basis of researching the formation mechanism and conditions for the hazards of loess slumping, the authors suggest corresponding engineering countermeasures.