Types and characteristics of loess landslides at Heifangtai Loess Plateau, China

Abstract

The Heifangtai Loess Plateau,which has a total area of 13 km2,is located in Gansu Province,China.Groundwater table in this loess plateau have been significantly raised since 1968 when the loess cover began to be artificially irrigated.Up to now,landslide events at 72 sites have occurred not only resulting in large economic loss but also exacerbating water and soil erosion that reduced plateau area badly.After several filed visits at Heifangtai Plateau from April,2006 to September,2007 and landslide Interpretation using IKONOS image,the following types of loess landslides there can be recognized:loess slide,loess earth-flow,loess-mudrock interface landslide,loess-mudrock bedding landslide and loess-mudrock incising landslide.The paper analyzed the developing characteristics of loess landslide based on the three dimension field scene overlapped by IKONOS image with DEM and the statistics for sliding directions.It is concluded that loess earth-flow took place along concave-terrain edge,north of Yehugou gully and loess-mudrock bedding landslides,controlled by mudrock incline of 180°190°,developed at sites which slope directions between 150°200°.The most important mechanisms of the loess landslides were wetting and softening induced by agricultural irrigation.In the last part,some research aspects for the future also been discussed.

20世紀60年代末期,為了安置劉家峽、鹽鍋峽庫區移民,在黑方臺建成了提水灌溉工程,造成地下水位上升,誘發了大量黃土滑坡。作者于2006-04～2007-09先后對黑方臺黃土滑坡進行了野外調查。利用IKONOS影像對黃土滑坡進行了遙感解譯,將其與研究區數字高程模型(DEM)進行疊加再現了滑坡場景。基于以上工作,首先對黑方臺黃土滑坡進行了較為系統的分類,包括黃土泥流、黃土滑動、黃土-泥巖接觸面滑坡、黃土-泥巖順層滑坡和黃土-泥巖切層滑坡。黃土泥流集中發育于野狐狗北部凹地形處;黃土-泥巖滑坡受基巖傾向控制,分布于坡向150°～200°的塬邊地段。農業灌溉補給地下水的增濕、軟化作用是黑方臺黃土滑坡的根本誘發原因。對黑方臺黃土滑坡機制的研究進行了展望。