Use of Multi-Electrode Electrical Resistivity to Define the Depth of the Landslide and the use of Isolated Tie-Back Plates to Stabilize the Landslide in Steep Terrain

摘要

An existing landslide located at the southeast corner of the Telluride Regional Airport has represented an on-going liability for the Airport, the Federal Aviation Administration and the Colorado Department of Transportation. A catastrophic failure of this landslide occurring in a manner similar to that which occurred at the Airport in 1987 has posed an on-going threat to closing Colorado State Highway 145 which is located below the slide area. The existing landslide was characterized as a series of multiple failed block areas located downhill of the airport runway that have occurred in severely weathered Mancos Shale. A total of 12 alternatives were evaluated to mitigate the landslide, including the preferred alternatives of either partial or total landslide removal. However, prior development left essentially no place on the airport property that would allow for the disposal of the landslide debris, and the closest off-site disposal area was approximately 40 miles from the site. As a result, in-situ stabilization of the landslide, including a primary system of isolated tie-back anchor plates with strand anchors, and a secondary system of high strength steel mesh and intermediate anchors was selected for the ultimate design to stabilize the landslide in place. For design purposes, geotechnical characterization of the slide area was accomplished through geological mapping, conventional borehole exploration and geophysics using multi-electrode resistivity (MER). The paper discusses the benefits of using MER and isolated tie-back anchor plates, particularly after discovery of survey error required redesign of the entire stabilization system half way through the project.