West Tunnel Portal and Rock Slopes
The main thoroughfare within Glacier National Park is the Going-to-the-Sun Road (GTSR). Landslide Technology (LT) is assisting the Federal Highway Administration (FHWA) with updating this roughly 50-mile long roadway. As the project has proceeded, several geotechnical issues have been addressed including slope stability; rehabilitation and reconstruction of stone masonry guardwalls, retaining walls and tunnel portals; roadway surfaces; material source development; subgrade and drainage improvements; and bridges.
One of the major aspects of this project has been rock slope evaluations for the GTSR. LT completed the Rockfall Hazard Rating System for the entire roadway, ultimately rating over 150 rock slopes.
Following the RHRS ratings, LT provided conceptual design and cost estimates for the top rated slopes. The park-allowed mitigation measures included scaling, rock bolts, and limited quantities of sculpted shotcrete. To preserve the historic nature of the GTSR, some mitigation elements, such as sculpted and tinted shotcrete, were tested outside the park to assess the aesthetics and ability to blend into the surrounding outcrops.
Final mitigation design plans, complete with specifications and annotated design photographs identifiying the locations of the mitigation measures, were prepared as part of the rockfall mitigation construction contract. The final design measures and engineer's estimate for each rockfall section were used to optimize the application of the department’s limited funds.