Possible Causes of Accelerating Landslide Motion in Confined Environment

Abstract

Effects of confinement on the mobility of rock avalanches characterised by a bipartite longitudinal debris distribution-the so called "Jumping" and "Secondary" rock avalanchesare discussed. Possible mechanisms causing accelerating debris motion after collision of the rockslide debris with the valley bottom or with the opposite valley slope are proposed. When the sliding surface daylights much above the foot of the slope rockslide really is projected into the air and its frontal part accelerates due to compression from the following debris and forms Jumping rock avalanche. If rapidly moving debris collides obliquely with an obstacle or enters into a constricted part of the valley, the momentum of the entire moving mass is transferred to the portion still retaining a possibility of further motion. This portion accelerates and forms a Secondary rock avalanche. These phenomena should be considered in rockslide hazard assessment and in statistical analysis of rock avalanches parameters such as volume and runout. KeywordsRock avalanche Á Runout Á Landslide dam Á Collision Á Momentum transfer 151