In 2017, the American Center for Mobility (ACM), built a U.S.-based connected and automated vehicle (CAV) research facility in Ypsilanti, Michigan, the heart of the automotive industry. The recently opened campus is a proving ground to the growing CAV technology market, allowing for product testing, development, validation, and certification. The 500-acre, driverless proving ground includes a 2.5-mile highway loop, two double overpasses, a railroad crossing, intersections, roundabouts, and a 704-foot long curved tunnel.
The curved tunnel, provided by Contech Engineered Solutions, is comprised of a 704 foot long, 49'-6" span x 24'-0" rise BridgeCor® Deep Corrugated Structural Plate tunnel with 9 - 4.5 degree elbows. In the preliminary design stages, Mannik & Smith coordinated with Contech’s team on different tunnel concepts. The ultimate goal was to create a tunnel where an automated vehicle enters the tunnel, but cannot identify the exit. Thus, the design of a lengthy, curved tunnel was paramount to the project.
Contech's BridgeCor solution was identified as the most cost effective option available to the market. The custom-shaped BridgeCor design was able to meet the required clearance box, included elbows to create a curved alignment and created a lightweight design allowing the use of a cast-in-place spread foundation. In addition, the entire structure was desiged for a Class II natural sand backfill, an economical, locally available material found locally by the contractors. The final design of the BridgeCor structure included cast-in-place headwalls, a lighting and mechanical system, and external waterproofing. By utilizing a BridgeCor 2-Radius Arch system, ACM was able to optimize overall construction costs with material, foundation, and installation savings.
The BridgeCor 2-Radius Arch system purchased by Z Contractors is 704 feet long and comprised of 163 rings with seven plates per each ring, a total of 1,141 plates. With pre-installation guidance from Contech, Z Contractors was able to assembly 8-9 rings per day, approximately 30’. With one crew divided into teams per side of the structure, each of the haunch pieces were assembled and then a three piece crown was then capped to minimize the number of bolts needed to be placed 24’ in the air. With Contech’s Winchester, Kentucky plant conveniently located within hours of the jobsite and constant communication with Z Contractors, Contech was able to deliver plates in pre-colored coded sections, keeping 20’ ahead of the crew at all times and eliminating any confusion as to which pieces were for what section. As the structure was assembled, each ring was verified by Z for both the 49’11” span and 24’0” rise to be achieved, each ring was built within 2” of the span/rise combination, well within tolerance of a structure of this size.
While Z Contractors was assembling the BridgeCor structure, Angelo Iafrate Construction Company began the backfill process, taking care to keep the assembled shape at least 75 ft away from the end of the tunnel. The backfill process required 8-10” lifts, compacted to 90% SPD in balanced loads. Iafrate was able to maintain the shape throughout the process and complete the structure with 3 ft of fill.
"We are excited to be open for testing and to have our founders already leveraging the assets of this facility," said John Maddox, CEO with ACM. "We have been moving rapidly, and along with good input from our founders, a great deal of work has gone into developing this site. Opening our doors is just the beginning as we continue to develop ACM into a global hub for CAV and future mobility technologies to put self-driving cars on America's roads safely."