Runout evaluation of Oso landslide with the material point method

Abstract

Long runout landslides can cause significant damage and represent one of the most important problems in geotechnical engineering. Understanding the mechanics of the landslide runout process is important for risk assessment and is challenging due to its complexities. This work examines the runout of the 22 March 2014 Oso, Washington, landslide. The Oso landslide is one of the worst landslide disasters in USA history with 43 fatalities. It occurred in multiple failure stages, involving several failure surfaces and significant soil softening, and travelled over 1 km across the valley. It initiated after a period of wet weather in an area prone to landslide movements. The triggering causes of the landslide movement are still under investigation. In this paper, the material point method is used to simulate the runout of the Oso landslide. This numerical tool is capable of modeling large deformation problems. It is used to investigate several hypothetical scenarios to identify key factors that contributed to the Oso landslide long runout distance.