关键词: 石碑塬黄土滑坡, 黄土液化特性, 微观结构, 液化应力比

Abstract: The Shibeiyuan landslide is a typically large loess flow slide which was triggered by Haiyuan earthquake in 1920. Understanding its behavior and mechanism is very important to study liquefied slope failures with long travel distance in the loess area. The in-situ investigation of the Shibeiyuan landslide shows that the saturated loess or the loess with high water content has high liquefaction and destructive potential which could cause liquefaction or flow slide under strong earthquake. The dynamic triaxial shear tests are performed on seven intact soil specimens taken from three places at the landslide. In addition, the scanning electron microscope (SEM) microscopic characteristics of the soil specimens are used to clarify the shear behaviors of these soil specimens. According to the results, the relation between water pore pressure and strain, as well as the relations between liquefied stress ratio and particle size, microstructure parameter, and degree of saturation are analyzed. The analytical results reveal that the liquefied stress ratio decreases and pore pressure response is stronger with the increasing of clay content. Meanwhile, the specimens with greater porosity have greater fractal dimension and less liquefied stress ratio. Moreover, the liquefied specimens are denser and its fractal dimension is greater compared to that before the liquefaction. Additionally, the degree of saturation has great influence on the state of interparticle cement and the microstructure in loess. The saturating process shows that the ionic concentration of the pore water is greater and the rupture of the interparticle contacts is easier when the degree of saturation becomes greater. As a result, the structural strength of the specimens decreases, leading to the decrease of the liquefaction stress ratio.

Key words: Shibeiyuan loess landslide, loess liquefaction characteristics, microstructure, liquefaction stress ratio