Launch of the tunnel boring machine for the Túnel Emisor Poniente II (TEP II) Project in Mexico marks not just a milestone for the project but is also a regional first for tunnelling in North America.
Work on the flood relief tunnelling scheme in Mexico City for the National Water Commission will be the first use of a crossover tunnel boring machine (TBM), designed to work in both rock and as an earth pressure balance machine, in North America.
Joint venture contractors Aldesa, Proacon and Recsa will use the Robbins TBM to drive the 5.9km long, 8.7m diameter tunnel through ground conditions that vary from volcanic rock to soft sands and clays.
The design of the TEP II machine is based on experience from past Robbins projects, including the Kargi Kizilirmak Hydroelectric Project in Turkey where a double shield TBM was specified based on expected ground conditions comprising fractured hard rock. Within 80 m of launch, the geology changed to blocky rock, sand, clays and water-bearing zones and the TBM underwent major modifications to enable the project to continue.
Modifications used at Kargi included a custom-built canopy drill and positioner for enhanced drilling and ground consolidation, gear reducers to adjust torque and RPM to changing ground conditions, and short stroke thrust jacks to double total thrust capabilities. Many of these modifications feature on the Crossover XRE TBM designed for the TEP II project.