PROJECT: GREENS CREEK MINE ACCESS ROAD STABILITY ASSESSMENT AND SLIDE REPAIR, Admiralty Island, Alaska

MSE Wall Construction
Construction of the MSE Wall

A single access road that accessed a mine site was experiencing landslide activity. The road was built in 1986. Photographs taken during construction suggest that the roadway was built by excavating into the relatively steep hillside and sidecasting the excavated materials to the outboard side.

The slope stability problems were first noted in winter 1999, when a heat plume was observed on the slope outside of the guardrail, which suggested a ground crack beneath the snow. In the following years there was evidence of additional slope distress indicated by displacement of the guardrail posts, cracks and sinkholes on the hillside and road surface, small slumps occurring in the road cut on the inboard side, seeps developing near the toe of the embankment, and falling rock occurring from a nearby exposed rock face.

Landslide Technology (LT) was retained to perform geotechnical reconnaissance of the problem areas, and to design landslide mitigation measures that could be constructed using locally-available fill materials and simple construction techniques. Following a subsurface investigation, LT designed a 100- by 14-foot MSE retaining wall that required only geogrid and facing material to be imported to the site and was easily constructed during a brief period when the main facilities were closed for maintenance. The construction was successfully completed over three work shifts. Much of the equipment and labor was provided by the mine's operations and maintenance crews.

Following this fast-track design and construction, LT has assisted the owner with a landslide and rockfall inventory of the access road in order to avoid costly road closures and unscheduled repairs.