In a recent project, University of Minnesota Duluth researchers determined effective methods for stabilizing slopes along Minnesota’s locally maintained roads and created a guide recommending slope stabilization methods for common site types. Previously, there was no guide for public works engineers to stabilize slopes of the scale typically seen along locally maintained roadways.
“We have recommended simple, effective methods for stabilizing at-risk sites and repairing common, recurring slope failures,” says David Saftner, an associate professor in UMD’s Department of Civil Engineering. “While no single method is appropriate for all situations, several methods have proven effective, and our guidebook succinctly summarizes those methods for local government engineers.”
Slope failures can block roads, cause safety hazards, and introduce preventable maintenance costs. When slope damage is severe, a geotechnical engineering firm must step in at some expense. But when damage is less severe, the county can often stabilize the slope using local materials and simple techniques. County road departments, however, often lack geotechnical expertise.
“This project created a user guide that local engineers can use right away to repair destabilized slopes,” says Blake Nelson, geotechnologies engineer in MnDOT’s Office of Materials and Road Research.
The project team followed a multi-step process combining site investigations, laboratory testing, and modeling. First, researchers identified and initially characterized slopes for further analysis using a survey sent to each county engineering department in the state; respondents identified stabilization methods and sites at which researchers could conduct field investigations to produce case studies. Next, the team identified and researched various stabilization methods, used laboratory testing to more accurately characterize soil collected from slopes of interest, and created models to investigate each slope stabilization method’s effect. Finally, researchers summarized the project’s findings and presented recommendations in their Slope Stabilization Guide.
Ultimately, this study and guide address the need for a consistent, logical approach to slope stabilization founded in research and experience. “Our guide was developed using resources not typically available to all county engineering and maintenance departments such as soils lab testing, advanced modeling, and geotechnical analysis,” Saftner says. “By implementing these recommendations, local government engineers can improve the stability of roadway embankments, minimize slope failure and associated damage, and decrease preventive maintenance costs.”
The Minnesota Local Road Research Board funded the project.
