Influences of Slope Angle on Propagation and Deposition of Laboratory Landslides

Abstract. Slope angle is an important influence on the motion characteristics and deposit morphologies of landslides. In this study, an advanced 3D scanner was used to study laboratory landslides at various slope angles. The laboratory landslides had different motion characteristics. An increase of the runout of the laboratory landslides with the slope angles meant that the amount of energy loss was great due to the collision of sliding mass at the slope break. The length and area of these laboratory landslides increased first and then decreased during their whole motion. The surface morphologies of the deposits differed according to the slope angles. At low slope angles, they exhibited a series of transverse ridges formed by overthrusting. At moderate slope angles, they exhibited conjugate troughs (X-shape wash) formed by shearing on the accumulation zone. At high slope angles, they exhibited a double-upheaval morphology formed by the rear portion of the sliding mass impacting the forward portion. A theoretical relationship between the apparent friction coefficient and slope angle is proposed, based on a hypothesis the ratio of energy dissipation occurring when an object collides with a plane is exponentially related to the acute angle between the object’s direction and the plane’s normal direction. The study will support studies on the morphological variation during the whole motion and mobility of landslides.