In most areas of northern China

there are two periods

that is

rainy and thawing periods

during which landslides and other geological disasters most frequently occur. At present

the researches on freezing-thawing landslides are still at the beginning

and the techniques of controlling this type of landslide are less studied than those of controlling rainfall landslides. The purpose of this study is to explore the fundamental characteristics and formation mechanism of the freezing-thawing landslides occurring in Gansu Province. The study shows that the seasonal freezing-thawing action is the main factor triggering this type of landslide

which not only causes failure strongly on the surface of slope

but also results in frozen perched water concentrated in the deep depth of slope. This action also contributes to the enlarging of the range of softening soil mass and the increasing of the dynamic and static water pressures

resulting in displacements of large soil mass of slope and finally the occurring of landslides.