Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

John D Quaranta

Committee Co-Chair

Hema J Siriwardane

Committee Member

John P Zaniewski

Abstract

This report presents the findings of an analysis of current highway rock cut slope design practices in West Virginia, in terms of rockfall mitigation, using the rockfall simulation computer software Colorado Rockfall Simulation Program Version 4.0. Additionally, this report presents the results of two case studies, conducted on highway rock cut slopes constructed in West Virginia, to determine the feasibility of reducing the number of geotechnical benches currently used in cut slope design and construction while still safely retaining rockfall and remaining structurally stable.;Two case studies were conducted on as-built rock cut slopes in West Virginia. The objective of the case studies was to determine if any amount of geotechnical benches could be removed from the current design and construction practices put forth by the WVDOT in an effort to reduce excavation and maintenance costs while maintaining structural stability and adequate rockfall retention. In addition to CRSP, a numerical modeling software (SoilVision SVSlope RTM) was used to determine the overall Factor of Safety of the slope section.;The first case study slope consisted mostly of hard, competent bedrock (limestone and sandstone), and initially had five benches. After modeling, it was found to have a Factor of Safety of 3.63, and a lowest on-slope rockfall retention of 75%. After three bench reduction trials, the final slope had one bench, a slope stability Factor of Safety of 1.47 and a lowest on-slope rockfall retention of 88%. The reduction in excavation for this slope section after removing four benches was 3670 ft2 per foot of slope length. The second case study slope was composed of interbedded layers of softer, more friable bedrock (siltstone and coal) and hard bedrock (limestone). The initial as-built slope had 6 benches, and was found to have a slope stability Factor of Safety of 1.26 and an on-slope rockfall retention of 92%. After four bench reduction trials, the final slope had two benches, a slope stability Factor of Safety of 1.48 and an on-slope rockfall retention of 88%. The reduction in excavation for this slope section after removing four benches was 4600 ft2 per foot of slope length. The results of the case study analyses showed that, with adequate bench widths and rockfall catchment ditches, backslope heights can be increased from the WVDOT-recommended 50 to 60 feet high to heights over 100 feet, while still retaining a safe amount of rockfall.

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