Investigation and Repair of a Landslide at Cass County Drain No. 10 in Fargo, North Dakota

摘要

On the morning of May 31, 2012 a landslide occurred into Cass County Drain No. 10 that blocked the flow of water through the drain, cutoff access to a local business, and severed a watermain that partially drained two water towers in the City of Fargo. County drains in the Red River Valley are typically on the order of about 15 feet deep and are often marked with relatively shallow landslides that are confined to the drain itself. This landslide was more significant and extended into both public and private property as illustrated in the aerial photo below. Given the lateral extents of the landslide as well as what was impacted by the slide, Cass County required not only a design for a repair of the drain but also an investigation into the likely cause of the landslide. This paper provides a summary of the subsurface investigation undertaken as well as the analytical modeling approach that evaluated the stress history in the vicinity of the landslide and the stability of the slope in the drain.