Structural Aspects of the Stabilization of Ten Mile Slide-Video

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The 10-Mile Slide stabilization project addressed a large, continually moving earthflow beside Highway 99, north of Lillooet, British Columbia. By 2016, movement had forced major traffic restrictions and made the highway costly to maintain. The solution combined 276 ground anchors installed progressively from the top of the slope with a retaining wall of 148 large-diameter piles near the highway. The wall used alternating concrete and steel-cased composite piles, tied together with steel and concrete walers and anchored through the concrete piles. Engineers analyzed the slope and wall using limit-equilibrium, finite-difference, and three-dimensional finite-element models, accounting for construction stages, ongoing movement, and earthquake effects. Construction was complicated by the moving ground and a COVID-related delay; additional loading during the delay caused further movement and required the retaining wall to be raised. Monitoring indicates the project has been successful, though continued sloughing below the highway is expected to expose much of the pile wall.

Keywords

10-Mile Slide

earthflow stabilization

Highway 99

ground anchors

retaining wall piles

geotechnical engineering