Rock Bolt Installation

Washougal River Road is a two-lane highway in southwest Washington. Boulders up to 3 feet in diameter were falling onto the roadway, creating a safety hazard along a 500-foot section of steep, 70-foot high road cuts.

Landslide Technology (LT) 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, LT performed rock slope stability analyses. Rock bolt forces were calculated and pseudo-static analyses were performed for seismic loading. Design 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 drainage improvements. Technical services included plans and specifications, field locating of rock bolts and construction observation at critical phases. Construction was completed within the original budget and one month ahead of schedule.