LANDSLIDE REMEDIATION AT TWO DIFFICULT SITES

Some landslides in soils have limited choices for stabilization. Restricted access, steep slope, continuing active slope movements, and environmental restrictions are some of the difficulties that can be encountered, usually precluding the use of simpler remedial practices, such as stabilizing berms or slope dewatering. This invited lecture presents two techniques that can be used in appropriate circumstances at "difficult" sites. Actual case histories illustrate the principles involved.

The first example is Portland General Electric's Faraday Canal landslide. After widening and deepening the canal in 1957, active landslide movements averaging about 1 foot (0.3m) per year were slowly constricting the channel and reducing the efficiency of the hydroelectric project. A three-step earthworks corrective procedure was implemented to maintain stability during reconstruction of the canal to its original cross-section. The slope has remained stable for the past 16 years.

The second example is the Goat Lick landslide in Glacier National Park. A 230-foot (70m) long section of highway was sliding towards the Flathead River, 275 feet (84m) vertically below the road, on a very steep slope. Due to the very sensitive environmental concerns at this site, a "Selective Stabilization" procedure was chosen. The remediation secured the safety of the road while allowing the active landslide below the road to remain unstabilized. A tied-back reinforced concrete shear pile wall was built. All construction work was confined to the road area, leaving the lower slope untouched.