US 421 SLOPE STABILIZATION ON PINE MOUNTAIN USING A TIEBACK WALL-Video

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Video Summary

The presentation covered slope stabilization on US 421 at Pine Mountain in southeastern Kentucky after a February 2019 storm triggered a large landslide. KYTC and FHWA funded a permanent tieback wall under the Emergency Relief program. Investigations found colluvial soil over Granger and Chattanooga shale, with groundwater generally 7–8 feet deep. Inclinometers measured 2–4 inches of movement, and the unstable mass extended roughly 800 feet across the slope.<br /><br />Limit-equilibrium analyses used inclinometer data to define the failure surface and establish wall loads that produced acceptable factors of safety. The design used a rectangular earth-pressure distribution and accounted for soil arching. The contractor completed the detailed design of the soldier-pile wall and anchors. The wall reached 46 feet in height, with piles embedded at least 18 feet into bedrock and two rows of tested, 12-strand anchors. The contract was awarded for approximately $5.9 million. Cement and fly ash requirements in the backfill addressed concerns about the shale’s potential acidity.

Keywords

slope stabilization

tieback wall

Pine Mountain landslide

soldier-pile wall

limit-equilibrium analysis

groundwater