LIQUEFACTION MECHANISM OF SANDY SILT OF TERRACE UNDER LANDSLIDE IMPACT

Recently, some scholars have noticed the liquefaction phenomenon of unsaturated sandy silt caused by the impact in the study of loess landslide in south Jingyang platform. This kind of liquefaction phenomenon is special because it is induced by a single impact load rather than a continuous cyclic load. The impact load has the characteristics of high strength, short time, and strong stress wave propagation effect. In order to study the mechanism of this impact liquefaction phenomenon, the paper built a landslide geological generalized model based on the geological background of loess landslide in south Jingyang platform and analyzed the variation of pore water pressure and total stress of sandy silt with different saturations in the same impact condition. The water content and shear strength of sandy silt after impact were also measured. The result shows that:(1)During impact load, the total stress and the pore water pressure in sandy silty are suddenly increased, and several pressure peaks occur because of the transfer of stress waves. While the wave disappears, the excess pore water pressure turns into the residual pore water pressure which remains stable for a period of time; (2)Under the impact of 80% and 90% saturation, sandy silty soil has different degrees of liquefaction at different layers, while sandy silty soil under the same condition of 70% saturation is not liquefied after impact; (3)The water in the lower part migrates to the upper part during and after the impact process. As a result, the water content of the surface soil increased, and the shear strength decreased; (4)The impact liquefaction mechanism of sandy silty is a rapidly destroying and recombining behavior of the original skeleton structure in an undrained condition, which causes the rapid accumulation of pore water pressure.