Use of Ring Nets for Slope Protection for Rockfall: End-of-Construction Report: SR 28 Rock Island Experimental Feature Study

The Washington State Department of Transportation (WSDOT) has used double-twisted hexagonal wire mesh and wire rope cable nets for several decades as slope protection to control rockfall initiating from slopes along state highways. Double-twisted hexagonal wire mesh has generally been applied to slopes with rock blocks less than 2 ft in size, while wire rope cable nets have been employed where larger blocks, typically up to 4-5 ft, are expected. In recent years, ring nets have been increasingly used for slope protection (drapery), mostly outside North America, to control large-sized rockfall. Because of the reported high strength of ring nets and the need to examine cost-competitive alternatives to cable nets, WSDOT proposed to evaluate ring nets for slope protection on a Federally-funded rockfall mitigation project. As outlined in the work plan submitted to FHWA, the study includes an evaluation of the ring net installation and an annual assessment of the performance for a 5-year period. This end-of-construction report documents the installation of the ring nets.