Robbins TBM launched to bore Turkey high-speed tunnel

The 3.05km-long tunnel will form part of Turkish State Railways’ 508km-long high-speed rail line connecting Polatli in Ankara Province with Izmir on the west coast.

Stored for the past seven years, the machine has numerous upgraded features to enable it to advance through mixed conditions including sandstone, gravelstone, claystone, and siltstone. In addition, contractor Kolin Construction expects occasional groundwater and weak rock (5-9MPa / 720-1,300psi UCS), with the potential for a gassy environment.

Robbins has designed the Crossover XRE with numerous features to cope with the conditions. The large-diameter design allows both screw conveyor and belt conveyor to remain in place, enabling swift conversion and operation in 100% EPB and hard-rock modes.

In EPB mode, the screw conveyor operates as in any typical EPB machine. A replaceable inner liner and replaceable carbide wear bits give abrasion protection to the screw system. The mixed-ground cutterhead is fitted with knife bits that can be switched out with disc cutters in harder conditions. The machine design includes a man lock for cutterhead inspection and changes, and mixing bars inside the mixing chamber.

To convert to hard-rock mode, the mixing bars and initial portion of the screw conveyor can be optionally retracted. EPB knife bits are then replaced by disc cutters on the cutterhead, and the EPB scrapers on the cutterhead are replaced by bucket lips. Muck paddles are installed in the cutterhead to allow the muck to fall into the muck chute. A hydraulic muck ring allows a chute attached to the bulkhead to move forward and down at a diagonal angle, allowing rock chips to be deposited in the chute and through the screw conveyor onto the TBM belt conveyor. To keep up production rates in both modes, the Robbins Torque-Shift System is used – a two-speed gearbox that enables efficient tunnelling in hard, mixed or soft ground.