BASIC TYPES AND CHARACTERISTICS OF MULTIPLE ROTATIONAL LANDSLIDES IN LOESS

Due to concentrated distribution,strong secondary and complex structure,multiple rotational landslides in loess is one of the most complicated landslide hazard types in the loess plateau.At first,this paper gives a definition of multiple rotational landslides in loess.So,it further studies the typical basic types,the characteristics and causes of multiple rotational landslides in the loess plateau of China in terms of hazards survey,geotechnical investigation and survey.Two types of multiple rotational loess landslides are the type of Jintai and the type of Heifangtai.They have different failure mechanisms and structures.The Jintai type of the landslides includes two classes of deep-seated multiple rotational-translational landslide and deep-seated multiple rotational landslide.The Heifangtai type of the landslides has mainly two classes of middle-shallow rotational loess landslides and multiple rotational bedding loess-mudstone landslides.The Jintai landslides are mostly large-scale landslides,composed by the three strata: near-horizontal thick layer pleistocene loess,gravel layer upper pleistocene terrace and pliocene red-hard clay.The analysis indicates that triggers of multiple rotational loess landslides include neotectonic movement,lateral erosion,strata lithology and structure,irrigation and seasonally freezing and thawing.Among the triggers,groundwater is the most inducing factor.The paper lays the foundation for mechanism study of multiple rotational loess landslides.