Formation of Landslide and Its shape

Abstract

The landslide face of plane shape is formed in the thin clay layer softened by the weathering of Tertiary layer. This clay layer is often called ‘latent slide face’, because the latent slide face has a basic factor in the landslide. Accordingly the landslide face is formed in the this part of clay by the occasion.Therefore, the length of landslide face in the latent slide face decides the shape of landslide, which is not a fortuitous resuit but the inevitable consequences. When the constants of shearing strength and physical properties of the clay layer are obtained by the soil tests, the length of landslide plane formed by the several causes is expressed by the following factors: that is, the average depth of the latent slide face h, the average inclination of the latent slide face θ, the coefficient of passive earth pressure in the upper part of the latent slide face kp, and the pore water pressure acting on the length of slide plane hw.It is very hard to measure the pore water pressure hw, when new landslide is caused by the heavey rain. Therefore, it is desirable that the shape of landslide plane should be used for the presumption of pore water pressure hw.