Landslides in a loess platform, North-West China

Frequent occurrence of landslides in the Chinese Loess Plateau has seriously threatened the urban and rural development. Heifangtai loess platform was selected as a case study for the current research. The platform surface is being largely irrigated since 1968. About 70 landslides of different types have occurred in the region including loess slides, loess flows, combined loess, and bedrock landslides along/across bedding planes. The loess slides occurred in the unsaturated soil and have a shallow failure depth. The loess flows initiated at the contact between loess and underlying clay and can travel a distance of more than 300m at a speed of up to 5m/s. Controlled by the topography of the underlying clay layer, the loess flows mainly occurred along the eastern margins of Heifangtai. The combined loess and bedrock landslides along bedding planes typically travel a distance of 30-60m at a speed of 0.002-0.005m/s with a volume of up to several million cubic meters. This type of landslide commonly occurred along the southern margins of Heifangtai, where the slope aspects are close to the inclination direction of the bedding planes of underlying bedrocks. Monitoring of perched water table in loess layer at the northern margin of Heifangtai shows the water table is rising at a speed of about 18cm/year.