US Highway 160, Wolf Creek Pass Landslide Stabilization, Mineral County, CO

Colorado Department of Transportation and Kirkham Michael and Associates

CDOT Region 5 had observed slope movement due to a landslide upslope of the roadway on the south side of the pass, which was causing cracking and bulging in the westbound highway section. Farther downhill of the landslide area was a cantilever retaining wall that was experiencing lateral movement resulting in distress to the roadway. Yeh and Associates was requested to conduct a geotechnical investigation for mitigation of the landslide and a separate investigation at the retaining wall to evaluate the cause of movement and provide recommendations for repair.

The landslide area was about 250 feet wide and our analysis indicated that the surficial glacial till deposits were sliding on the bedrock surface with movement being associated with rises in groundwater levels in the spring. We provided alternatives for landslide mitigation and CDOT selected the installation of horizontal drains with ground anchors alternative. Our investigation indicated the retaining wall was placed on a loose or uncompacted foundation material, which had settled resulting in the wall deflection. Surface water infiltration at the toe of the wall may have also contributed to the settlement.

We recommended two alternatives for mitigating the retaining wall failure and CDOT selected compaction grouting of the loose foundation materials. Yeh and Associates subsequently designed the repairs for both areas and provided design drawings and specifications for the repair alternatives selected. During construction, we provided construction observation and materials testing services.

Yeh's key personnel that worked on the project included Rick Andrew who was the project manager, Ben Arndt was the project engineer and Tom Allen oversaw the construction observation and testing services.