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Rockfall hazard assessment and rating Rock slope stabilization design Scaling, rock bolts, shotcrete and draped mesh Washougal River Road is a two-lane highway on the right bank of Washougal River in southwest Washington. Boulders up to 3 feet in diameter were falling into the roadway, creating a safety hazard along a 500-foot section of steep, 70-foot high road cut. Landslide Technology was retained by Clark County to perform a rockfall hazard assessment and to develop conceptual options to stabilize the slope. Services included: geologic reconnaissance, rock slope mapping, and identification of specific rockfall hazards. Recommendations were provided for immediate, short-term, and long-term hazard mitigation. The Rockfall Hazard Rating System was also used to prioritize the slope hazard. In a second phase of services, Landslide Technology performed rock slope stability analyses for planar slide and toppling blocks. Necessary rock bolt forces were calculated and pseudo-static analyses were performed for seismic loading. Designed stabilization measures included clearing and scaling of the rock face, rock bolt slope reinforcement and block stabilization, shotcrete protection of weathered zones, rockfall control with draped wire mesh, and ditch drainage improvement. Technical services also included plans and specifications, field location of rock bolts and construction observation at critical phases. Construction was completed within the original budget and one month ahead of schedule. |
