Beartooth Highway, Shoshone National Forest, WY

FHWA Western Federal Lands Highway Division and PBS&J

The Beartooth Highway project involved about 35 miles of roadway improvements including alignment, grade, and widening. The project involved installing drainage structures, installing subsurface drainage features, subgrade stabilization measures, replacement of four existing bridges and construction of two new bridges, construction of retaining walls for widening and reconstruction of asphalt pavement on the roadway, adjacent parking areas and pullouts, as necessary to meet current design practice.

Yeh and Associates was requested to evaluate and provide retaining wall designs based on the subsurface conditions and slope cross sections previously developed. Design evaluation included internal, external and global stability of the proposed fill retaining wall systems. Our work also included coordinating geotechnical design with roadway, hydraulic, and structural designs and review of final construction documents for conformance with design assumptions.

Based on our evaluation and analysis, we presented a wall design to CFLHD that extended the MSE wall reinforcement lengths and varied embedment depths to satisfy AASHTO global and external stability requirements. We also proposed low-pressure, low-slump grouting as an additional subgrade improvement along the proposed higher MSE walls sections, where there were potentially loose materials with voids, deeper bedrock profiles, and steeper slope profiles in front of the wall, to decrease post-construction settlement and fill potential voids between boulders to reduce movement.

Yeh and Associates work provided an alternate design to previously proposed micro-pile footings to support the MSE wall at the same locations. Based on our alternative that varied MSE embedment depths, geogrid lengths, and used of low-pressure subgrade grouting techniques, the costs of the project were substantially reduced and still met or exceeded minimum AASTHO guidelines for wall stability.

Yeh’s key personnel that worked on the project included Shan-Tai Yeh who was the QA/QC reviewer, Rick Andrew was the project manager and Ben Arndt was the project engineer for the investigation and design.