Abstract

A 180-ft-wide (54.4-m-wide) landslide occurred along the north side of Foxridge Drive (Mission, Kansas) in July 2001. The earthen mass had moved laterally and downward approximately 2 ft (0.6 m). Additional movement during the following months indicated the landslide was threatening stability of the north edge of the roadway. In addition, the road was scheduled to be widened by approximately 10 ft (3.0 m) in the near future. Therefore, repair of the slope was critical to the stability of the road and the future widening. A phased subsurface investigation revealed subsurface conditions generally consisting of fill overlying alternating layers of limestone and shale. An inclinometer was installed to monitor further slope movement and evaluate the location of the slip surface. Exploratory drilling, inclinometer monitoring, and modeling of the slope indicated the most probable slip surface was positioned at the contact between the fill and underlying shale. The landslide was likely caused by a rise in the groundwater level resulting from a wetter than normal spring. A geogrid reinforced earth system was designed to repair the slope. The base of the repair consisted of crushed rock backfill with welded-wire baskets at the face to provide an independent toe wall. The upper portion of the design section consisted of reinforced clay and crushed shale backfill. Topsoil was brought in to provide a medium for re-vegetation.

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