关键词: 黄土滑坡, 特征, 高速远程, 农业灌溉, 地下水, 黑方台

Abstract: In the morning of April 29,2015,two large-scale loess landslides occurred continuously at Luojiapo of Dangchuan Village of Yongjing County,Gansu province. The total volume is about 65×10⁴m³,with the maximum sliding distance of 630 m,and 14 households and 3 factories destroyed. Based on the analyses of detailed investigation in situ,sampling test,1：500 topographic survey and video data of the landslides,the landslide features, formation mechanisms and sliding processes are discussed about. It is believed that the Luojiapo Landslides are loess landslide induced by irrigation. The result show that the first landslide had experienced deformation accumulation for two years,and then collapsed with high speed and long distance. The second landslide had experienced deformation accumulation only 3 hours,sliding block by block,lasting a long time and a complicated process,which was low speed and long distant slide. The basal condition of landslide is high and steep terrain and soil of low strength and water sensitivity;artificial factor is long-term agricultural irrigation in the loess platform tableland. When the thickness of saturated soft foundation reaches about 20 m,in case of a large number of water infiltrating in,it will lower the shear strength,and then lead to instability of the loess. The main conditions of loess having high-speed sliding for a long distance are a high position of landslide burst export,a large sliding potential with good release condition and a steep slope at the bottom. It is very important to have an excess pore water pressure caused by saturated soft clay at the bottom of the sliding body,resulting in low friction effect due to liquefaction.

Key words: loess landslide, characteristics, high-speed & long distance, agricultural irrigation, groundwater, Heifangtai