By: Contech Engineered Solutions
In 2019, the West Plains Mining expansion required a double-loop rail system expansion tying into the Norfolk Southern Railroad system servicing east and west destinations. As part of the new track
layout, a tunnel under Old US-24 was needed to allow connection to the Norfolk Southern system east of the mining property. A significant amount of coordination was needed between Wabash County Road Department and the West Plains Mines to limit the local impact of the heavily-traveled roadway.
The West Plains Mining team coordinated with Contech Engineered Solutions to create a tunnel solution. The team reviewed options of a precast arch system, a deep-corrugation structural plate arch system and an at-grade truss structure. The primary design drivers for the structure design was the Norfolk Southern required clearance area for rail and safety, a proposed 50 ft vertical dimension between the final rail height and the current roadway height, an existing 3-span bridge situated less than 80 ft from the proposed tunnel, and the ability for the WPM team to blast the required opening in the limestone. After review of the proposed design and balanced with the economic review of total construction costs, the team selected a 30 ft deep corrugation round structure at 200 feet in length as the best option for this site.
Balkema Excavating completed the backfill of the tunnel and constructed the MSE Wall. The benefit of working in a mining operation was the available of select backfill material made specifically to the requirements of the tunnel & wall system. The challenge was completing the backfill within the 45 ft channel, between the 30 ft tunnel system. At times the team had approximately 8 ft of area to backfill and compact around the structure.
The tunnel channel was blasted and aggregate removed during the month of January 2020, and the tunnel started construction in mid-February. Old US-24 was open to traffic by June 2020.