Abstract: In the beginning of 2008, South China encountered the rare extreme snow climate; and in this period many geological hazards happened. In order to study the correlation between the extreme snow climate and geological hazard, this paper explored the evolution characteristics of homogeneous loose debris slope in the condition of extreme snow hazard. The landslide triggered by snowmelt is compared with rainfall to obtain the similarities and differences and then the general law of snowmelt triggering landslide is analyzed through a specific example. Two physical quantities named degree-day factor and snow rainfall equivalent are used to establish the simplified effective snowmelt model based on the characteristics of extreme snow climate in Southern China. The evolution characteristics of the debris slope are simulated from seepage, stability and deformation under the different snow rainfall equivalent proposed above. The results show that a certain snowmelt rate and quantity have no influence on the seepage of the slope. With the snowmelt continuing, the metric suction in the unsaturated zone decreases gradually which causes the whole stability decreasing. The horizontal and vertical displacements of the slope surface increase gradually and the deformation of the front is larger than the back in the horizontal direction as well as the down dislocation in the back and protrusion in the front. After a time of snowmelt the slope fails and slides.

Key words: extreme snow hazard, snowmelt, degree-day factor, snow rainfall equivalent, loose debris slope, evolution