STEEP BRIDGE ABUTMENTS

Shoring up steep roadway embankments and bridge abutments, susceptible to erosion from saturated soils or sheet flow runoff, poses challenges for project engineers. Incorporating the right structural erosion-protection system that assures a high resistance to erosive forces, low maintenance, and aesthetic integration with the natural surroundings are important considerations in slope designs.

The GEOWEB® 3D soil confinement system is that proven solution. By stabilizing infill in the system’s deep, interconnected network of cells, downward migration is prevented on slopes to 1h:1v—and greater. Infill confined within the geocellular network remains stable, and minimally affected by surface runoff—consequently limiting potential for erosion rills to develop.

Project Case Study: Minnesota (MN) DOT Bridge Design

I-90 Bridge, La Crosse, WI to La Crescent, MN

The goal of a three-year, $187.5 million MN DOT interchange project was to build a new, structurally sound, river crossing bridge that met current structural and geometric standards over a vital regional river crossing and to improve capacity and access between two highways. Aesthetics were an important consideration.

On the steeper slopes at the bridge abutment and around the bridge piers, the GEOWEB system addressed both structural and aesthetic design requirements. Calculations and anchor spacing recommendations for 11 different areas of varying slope lengths and angles were provided by Presto’s engineering team. Two different in ll materials were used:

• Aggregate: 50,000 sq ft of tan GEOWEB material closely matched the local aggregate color. Slopes varied between 2H:1V and 1.5H:1V, up to 45 feet vertically, under bridges. Lack of sunlight and moisture prohibited use of vegetation in these areas.
• Topsoil/Vegetation: 100,000 sq ft of black GEOWEB mate- rial with topsoil, seeded and finished with an erosion control blanket. Slopes varied between 2.5H:1V and 3.5H:1V.

The completed embankments were fully stabilized—and blended harmoniously with the natural surroundings created by the bluff and river environment.

Article content credits to MN DOT-WI DOT, SRF Consulting Group MnDOT-Winona