George Washington Memorial Parkway
Location
Arlington County, VA
Client
Federal Highway Administration
Services Provided
Rock Slope Stability Evaluation
Rockfall Hazard Assessment Geostructural Design
Plans and Specifications
Engineering Cost Estimate
Geologic Structure Mapping
Field Investigation
Project Overview
Schnabel’s innovative rock slope stabilization design won the Grand Design award in the 2010 ACEC/MW Engineering Excellence Awards (EEA) competition, and was also recognized as a 2010 EEA National Finalist. Schnabel’s design achieved the client and owner’s dual objective – to protect the traveling public from rockfall while preserving the aesthetics of this scenic federal highway.
In 2002, the 35-ft high, 240-ft long rock cut slope released several large rock blocks onto the shoulder and into the travel lanes. The rockfall damaged curb and pavement, and disrupted commuter traffic. Schnabel provided geotechnical and geostructural engineering services to investigate the cause of the slope failure, assessed the future rockfall hazard potential, developed conceptual stabilization design alternatives and comparative costs estimates, and prepared final design plans and specifications for the selected concept design.
Schnabel used a new technique, rock gluing, as the primary method of mechanical stabilization in lieu of traditional methods, such as rock anchors and nets, which would have dramatically altered the natural slope aesthetics. Rock gluing is the method of injecting polyurethane resin grout into a rock mass to improve the structural integrity and slope stability internally with little surface expression.
Schnabel’s new approach helped Eastern Federal Lands Highway Division (EFLHD) and the National Park Service (NPS) achieve their goal of improving slope stability while preserving the highway landscape. It was the first designed use of the rock gluing technique by EFLHD. The major innovation for this project was that Schnabel developed a new method to quantify slope stability improvements providing a basis for design where none existed before.