TYPES AND CHARACTERISTICS OF LOESS LANDSLIDES AND COLLAPSES IN LLIANG AREA OF SHANXI PROVINCE

LLliang area is located in West Shanxi loess plateau where geological environment is rather fragile, geo-hazards occur continually and the loess landslides and collapses cause enormous casualties and heavy economic losses. This paper is based on field investigations and combined with in-situ and laboratory tests. It studies the types and characteristics of landslides and collapses in this area. According to the formation lithology, geological structure and the position of sliding plane, loess landslides in LLliang area are divided into two basic types: Q3 homogeneous loess landslide and Q3-Q2-N2 landslide occurred in the composite structure of layers. Then the failure modes of loess collapses are classified as toppling, subsiding and stripping collapse. In the space, the loess landslides and collapses in LLliang area are distributed in four counties(Liuling, Lishi, Zhongyang and Shilou) and developed in belts along the highways and railways. In time, loess landslides and collapses have an obvious annual variation law and occur in flood period(from June to October),especially in the main flood season(from July to August).Finally, the mechanism of the Q3-Q2-N2 landslide in the composite structure is discussed, which shows that manual excavation and rainfall infiltration are the two main induced factors.