Abstract

A new method has been developed to stabilize slopes and landslides using driven, geotextile wick drains rather than drilled polyvinyl chloride or steel drains. Compared to drilled horizontal drains, wick drains can be significantly deformed without rupturing. They resist clogging, and they can be installed quickly and economically by workers with no previous training. Since 1998, more than 170 drains, totaling more than 2,600 m (8,600 ft) in length, have been installed at eight sites in Missouri, Colorado, and Indiana. At three of the sites, drains were installed at a density and layout considered to be appropriate for full-scale stabilization: 27 to 44 drains were driven at each site, averaging 15 to 20 m (50–70 ft) in length. A method was developed to accurately estimate the groundwater-table profile after drain installation, and computer slope-stability analysis using this method showed significant increases (10–40 percent) in factors of safety after drain installation. The limitations of the methodology should be recognized: it may be applied in specific situations requiring relatively short (<30–45 m, or <100–150 ft) drains in materials ranging from soft to very stiff (up to 30 blows/ft in standard penetration tests). The potential effectiveness of drainage as a mitigation option should be verified through analysis of site geology and hydrogeology before drain installation.

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