US-50 Big Horn Sheep Canyon, Fremont County, Colorado A Rockfall Mitigation Case Study

摘要

US-50 extends west to east in Colorado from Grand Junction to Pueblo and beyond traversing through the rugged terrain of the Central Rocky Mountains and is lined with steep natural and constructed rock slopes. A rockfall mitigation analysis and design was requested by the Colorado Department of Transportation (CDOT) for an existing rock slope on US-50 between MP 242.2 and MP 242.6 near Coaldale in Central Colorado. The rock slope ranges in height from 100 to 300 feet and forms blind corners with limited rockfall catchment zones. The Arkansas River is immediately north of and parallels the road and rock slope.In the spring of 2007, the authors conducted detailed geologic mapping of the rock slope using mountaineering techniques. Based on our mapping and mitigation analysis, blocks of concern and areas of rockfall were identified along the slope and recommendations for mitigation were developed. In conjunction with CDOT, detailed design plans and specifications for mitigation of the rockfall hazards were prepared. Mitigation began in September 2008 to stabilize the areas of concern. Because of the proximity of the Arkansas River, netting was suspended from a crane during scaling to reduce the potential for rockfall into the river. Modified rockfall nets were suspended in gullies and large rock blocks were anchored to the slope. Additionally, a joint team from CDOT and Kleinfelder engineers installed crack monitoring devices along the base and side of a large potentially unstable block to remotely monitor movement because of its size and location on the slope.