Characteristics and Forming Mechanisms of the Plateau-Edge Cracks and Their Significance to Loess Landslides

Loess landslide is the most catastrophic geohazard in Northwestern China. Plateau-edge crack is one of the representative characteristics for most loess landslides. Groundwater table in the South Jingyang Plateau, Shaanxi Province has been significantly raised since 1976 and more than 50 landslide events have occurred at 27 sites, resulting in large economic loss and numerous deaths. Based on field survey and measurements of cracks at South Jingyang Plateau, it can be concluded that 28 cracks with a total length of 1424 m were developed at the edge of the study area. Based on the topographic features, the cracks can be classified as "U" model, "W" model and "Z" model. At the initial stage, cracks are caused by the accumulated small strain of the slope soils. The present features of cracks can only reflect the present geological conditions. The forming mechanisms of "U" model, "W" model and "Z" model cracks are, thus, very similar to but not the above mentioned mechanism. Cracks developed change soil stress state and make it to be near the collapse surface, and then a small load or water infiltration can induce landslides. Cracks that can collect surface water and increase the possibility of rain or irrigation-induced landslides. Cracks also have important significance to loess Landslides evolution and "group distribution" characteristics.