Back-to-Back Geosynthetic Reinforced MSE Wall Supporting Elevated Dual Railroad Tracks

摘要

A newly developed mechanically stabilized earth (MSE) system consisting of large precast block with a mechanical connection using narrow geosynthetic reinforcement provided a cost effective solution to a challenging project. Canadian National (CN) Railway needed to switch an at grade rail crossing with a commuter system to an elevated crossing. Due to the overhead catenary electrical wire system of the commuter rail line, a metallic reinforced MSE wall system could not be used. Geosynthetic reinforced MSE wall systems are generally more cost effective than metallic reinforced systems, and there is no concern using geosynthetic reinforcement near a catenary system. This unique project was one of the first to use this positive connection system with continuous reinforcement through the facing block. It was also the first geosythetic MSE wall system supporting dual railroad tracks with less than 1 degree face batter. The MSE system uses geogrid soil reinforcement in 300 mm (1 ft) wide strips. Because the reinforcement is in strips instead of full sheets, the MSE structure is designed with a reinforcement coverage ratio of 50% instead of 100% which would be typical of full sheets. The MSE abutment is approximately 6.4 m (21 ft) tall at the bridge structure. The wall is being monitored by surveying to observe performance during and post construction. The wall sections were completed at the end of 2012. This paper will present the design, construction and monitoring of this historic project.