One of the most effective options to stabilize landslides is to reduce the amount of water they contain by installing horizontal drains. A new type of horizontal drain material, geosynthetic wick drains, and a new installation method, driving drains rather than drilling them, were evaluated. Horizontal wick drains offer several advantages over conventional horizontal drains: They resist clogging, are inexpensive, may be deformed without rupture, and may be installed by unskilled laborers with a minimal investment in equipment. More than 100 drains were installed at eight sites in Missouri, Colorado, and Indiana using bulldozers, backhoes, and standard wick drain-driving cranes. Drains have been driven 30 m through materials with standard penetration test values as high as 28. Both experience and research indicate that drains should be installed in clusters that fan outward, aiming for average spacing of 8 m for typical clayey soils. As with drilled drains, initially some drains are expected to be dry, although these drains often become active during wet periods and serve as an important part of the overall slope stabilization scheme. Drain effectiveness is expected to build over the first few years as the effects of soil smear during drain installation are removed, peaking at 3 to 6 years after installation. The effectiveness is then expected to decrease as fine particles slowly clog the drain pores. From published tests, clogging appears to occur slowly enough in typical clay soils that the drain life is comparable with the project life.

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.

No abstract

for 5 years in the areas of MEMS, nanotechnology and advanced materials. He has served as a guest editor/editorial board of journals including Journals of Materials Science. Dr. Allameh holds a PhD from The Ohio State University. He has published over 70 scientific papers/book chapters.

No abstract