Case Studies on Rockfall Mitigation and Rock Slope Stabilization in California, Tennessee, Virginia, and Vermont

摘要

Rockfall constitutes a major hazard along our nation's roadways and a nagging liability to our maintenance and engineering departments. Recurring cleanup and repair costs have stressed dwindling maintenance budgets. The extensive nature of the problem precludes repairing and mitigating every possible site, but new and innovative mitigation technologies and contracting techniques can serve to stretch tight budgets. There are many methods that can be used to stabilize a rock slope. These include altering the slope geometry, installing drains, adding reinforcement, or a combination of these methods. The challenge for engineers is to design a method that can be installed with little or no impact to the traveling public, is expedited through innovative contracting methods, limits the disturbance to environmentally sensitive areas, and maintains an aesthetically pleasant appearance and appropriate service life. This presentation covers four case studies that highlight innovative technology and innovative contracting methods for rockfall mitigation. The case studies include a project for the United States Army Corps of Engineers near Chowchilla, CA using design/build/warranty contracting and post-tensioned rock bolts with Maccaferri B600 mesh facing; a project for the Tennessee Department of Transportation near Maryville, TN using rock dowels and Geobrugg's high-capacity Tecco? mesh facing; a design/build project for the Virginia Department of Transportation near Hillsville, VA using a shear dowel array encased in reinforced shotcrete overlying a drilled drainage array; and an emergency design/build rockfall mitigation project for the Vermont Agency of Transportation that used a shear key, scaling, vegetation removal, rock dowels, and both wet and dry mix shotcrete.