Characteristics and mechanism of snow-melt loess landslides in Yili Valley, Xinjiang autonomous region

In the previous decades, loess landslides with amount of 1992 occurred in Yili valley, Xinjiang autonomous region of China. These landslides have caused a series of engineering disasters. However, comprehensive report regarding the characteristics of these landslides has not been made, and the sliding mechanism is also not thoroughly clarified. In order to address these issues, extensive field surveys and laboratory tests have been conducted. These results conclude that the length/width, sliding thickness, altitude and the gradient of these loess landslides mostly locate in the range of 10–300 m, 0.5–20 m, 1000–2500 m and 10°–50° respectively. Additionally, these loess landslides in Yili belong to the snow-melt landslides, which primarily occurred in the snow-melt season from yearly mid-February to mid-May. For these snow-melt landslides, the sliding mechanism includes following parts: freeze-thawing action notably weakens the shear strength of superficial loess, resulting in the sliding of superficial loess layer. Moreover, freeze-thawing also promotes the inner-fissures growth in superficial loess, increasing its hydraulic conductivity and accelerating the infiltration of melted snow-water or rainfall into lower loess layer. As lower loess becomes saturated, its strength diminishes significantly, further inducing the deep sliding.