Efficient Rock Slope Design during Construction of a State Highway Safety Enhancement Project
In summer of 2020, the Idaho Transportation Department (ITD) began construction work on a safety-enhancement project of SH-55 between Smiths Ferry and Round Valley along the North Fork of the Payette River approximately 50 miles north of Boise. Work to widen and straighten the road included excavating 9 distinct cut slopes in weathered granodiorite using controlled blasting techniques along the approximately one-mile section of roadway. In the spring of 2021, a rockslide from a cut slope under construction impacted the roadway and closed the highway for over a week. Soon after that rockslide a wedge at a different cut also failed, posing a serious risk to workers. McMillen Jacobs Associates (MJA), which had been contributing to the project as a blasting consultant, was retained by ITD following the slope failures to redesign the rock cuts to reduce the potential for additional failures and maintain a safe working environment. MJA arrived on site in March 2021 and in a condensed time frame conducted geologic assessment and mapping using rope access safety techniques. MJA then performed kinematic stability analyses and slope redesigns at each cut slope based on mapped discontinuity orientations to recommend slope cut angles. As cuts were excavated and final slopes exposed, MJA identified potentially unstable rock planes and wedges and, through a combination of field inspection and limit equilibrium analyses, developed appropriate mitigation strategies. This paper presents the techniques, strategy, and workflow utilized to provide a meaningful slope redesign during active construction and within project constraints.
- Record URL:
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Supplemental Notes:
- Copyright © 2022 Highway Geology Symposium (HGS). Abstract reprinted with permission of the HGS.
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Corporate Authors:
Highway Geology Symposium
, United States -
Authors:
- Ferguson, Luke
- Guzek, Ethan
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Conference:
- 71st Highway Geology Symposium
- Location: Asheville North Carolina, United States
- Date: 2022-5-23 to 2022-5-25
- Publication Date: 2022
Language
- English
Media Info
- Media Type: Digital/other
- Features: Figures; Photos; References; Tables;
- Pagination: pp 67-82
- Monograph Title: Proceedings of the 71st Highway Geology Symposium (HGS 2022)
Subject/Index Terms
- TRT Terms: Embankments; Equilibrium methods (Structural analysis); Geological surveying; Highway design; Rockslides; Slope failure
- Identifier Terms: Idaho Department of Transportation
- Geographic Terms: Boise (Idaho)
- Subject Areas: Construction; Design; Geotechnology; Highways;
Filing Info
- Accession Number: 01852517
- Record Type: Publication
- Files: TRIS
- Created Date: Jul 21 2022 1:39PM