CAUSES OF GAOLOUCUN LOESS FLOWSLIDE IN HUAXIAN COUNTY, SHAANXI PROVINCE

Rapid loess flowslides induced by irrigation often occur in the loess irrigation area, which have resulted in serious damages to farmlands, residential houses and loss of lives. A typical case of the Gaolou flowslide in Guanzhong irrigation area, Shaanxi Province of China, was investigated. Laboratory tests suggest that the loess flowslide had a loose structure and that the saturated water content was higher than the liquid limit. As the loess slope started to fail, the saturated loess of the sliding zone quickly fluidized and then flowed on the relative dry-hard path because the loess structure was damaged by the shear force to produce a high excess pore pressure in the lower portion of the displaced mass. Excess pore pressure was produced between the displaced mass and the ground surface because of pore pressure dissipation on the dry ground. So the shearing zone was within the lower portion of the displaced mass other than on the ground surface, which made part of the displaced mass cohere on the ground as observed at the site. The triaxial tests for the loess specimens suggest that fluidization occurred at the source area in the beginning and maintains in the moving process, which produced a quick and long run-out flow. The modified Sassa K.simulation model for landslide motion is applied to simulate the motion scenarios of this case. And the simulated results fit the actual ones of site investigation.