ABSTRACT
Colluvial landslides refer to the landslides that occurred in the quaternary system or in the relative loose cumulative stratum before the Quaternary period. Colluvial landslides were frequently triggered by rainstorms. Colluvial soils are generally characterized by loose composition, large porosity and high permeability due to specific compositions of the sliding mass. Many colluvial soils are widely and gap-graded with a small sand fraction and show a bimodal feature in grain size distribution. The hydraulic properties of colluvial soils with different coarse contents are measured and used to analyze the stability of a colluvial soil slope during rainfall. W. G. Holtz & H. J. Gibbs conducted an experimental study and suggested the relation between the coarse frictions and the shear strength of soils mixed from gravel and clayey slity sand. The water infiltrated in the upper soils flows to the lower soils and the water table beneath the slope rises slightly in a limited period after the rain.
