Tunnel machine manufacturer Robbins has launched the first of its new Crossover TBM series machines on a project in Mexico City.

The 28.5-foot XRE TBM was assembled onsite, beginning the project on the Túnel Emisor Poniente II (TEP II) project in August. The TEP II is a major wastewater project by joint venture contractor ALDESA/PROACON/RECSA. The 3.7-mile tunnel will wind through variable conditions, including competent and weathered volcanic rock, soft sand and clay. The “crossover” TBM was selected for the project because it handles two modes: rock and earth pressure balance. Standard TBMs can lose efficiency in such varied conditions, but the Crossover TBM is specially designed and field tested to handle such changes. Features include a single-direction cutterhead for abrasive ground conditions and specialized gearboxes for addition torque at low rpm conditions, like fault zones and soft ground, and high rpm for rock boring.

“In my opinion, the best part about the design of this TBM is the cutterhead; it is very robust,” said Sebastián Gallego Murillo, TEP II production manager for PROACON. The biggest challenge on the TEP II project, he said, would come near the end of the tunnel drive. “We expect to convert [from hard rock] to EPB mode due to the soils in this area. We will need to change out the cutters and modify the cutterhead.”

The TEP II project is 20 years in the making. “This tunnel will reduce flooding in the west and northwest areas of the Valley of Mexico, and increase wastewater capacity. It will benefit three municipalities that are home to 2.1 million people,” said Gallego. The three areas are prone to wastewater overflows of more than 6 feet during the region’s rainy season.

The Robbins Company has more than 60 years of experience in underground construction and excavation. For more information, visit www.therobbinscompany.com.