In the Spring of 1983, a large landslide occurred near the town of Thistle, Utah which blocked major transportation routes and impounded the Spanish Fork River, inundating the town with 200 feet of water. While much attention has been given to the slide and its impact, very little has been directed toward a quantitative understanding of its causes. An analysis was performed of the Thistle landslide using the SEEPSLOPE finite element system in order to evaluate the mechanisms, factors, and causes of the failure. An elastic, perfectly-plastic stress-strain curve was employed in the analysis to model the behavior of the overconsolidated clay soils. It is concluded that the landslide was a compound, progressive failure which initiated at the toe and progressed uphill. Seepage forces played a significant role in the failure
