The Function of Vegetation on Landslide Stability: the Reasons Caused the Qianjiangping Landslide in Three Gorges Reservoir Area

Many landslides occurred after storing water of Three Gorges Reservoir. In order to determine the action of vegetation on landslide stability, we investigated a series of features of the nature forest, orange forest and landslide, such as vegetation coverage, soil volume weights, the distribution of roots, dead roots in soil and the shear strength of root - soil composite systems in Qianjiangping landslide regions in Three Gorges Reservoir Area (TGRA). Our results showed that, in nature forest and orange forest, the vegetation coverage, species number and root content in soil were higher than on landslide. When soil water content is saturated, the shear strength of root - soil composite systems increases linearly with increasing vertical pressure. The shear strength, cohesion and internal friction angle of nature forest root - soil composite systems were significantly higher than those of orange forest and landslide. Those results indicated that the nature vegetation could much enhance the stability of landslide, while the most major local man - made forest in TGRA, orange forest could play less important role in enhancing the stability of slope. In order to protect the environmental condition and lessen the occurrence of landslides, we should adopt available measures to protect the nature forest in existence in TGRA.