By Lynda Myer
The Eşme-Salihli Railway Tunnel is going to excavated by a Robbins XRE TBM, this TBM that has 13.77 m (45.18 ft) diameter recently is launched in spring 2021 in Eşme, Turkey. The large machine is digging the Eşme-Salihli Railway Tunnel with 3.05 km (1.90 mi) length through mixed conditions including sandstone, gravel stone, claystone, and siltstone. According to contractor Kolin Construction’s estimation the possible uncertainties along this path are: some occasional groundwater and weak rock between 5 to 9 MPa (720 to 1,300 psi) UCS, with the potential for a gas emission.
Following some updates to systems to ensure they have the modern safety and efficiency standards, this gigantic TBM was started up after more than seven years in storage.
“I am very happy that the TBM has been launched. Up to now, the machine has bored nearly 500 m (1,600 ft) in gneiss and mudstone. This is an opportunity for Robbins to prove that large diameter TBMs can bore in such tunnels, even in very complex geology and difficult ground conditions,” said Yunus Alpagut of ATES, Robbins’ Turkish subsidiary.
He also added: “Recently, there have been large diameter, non-Robbins machines that have failed at projects such as the high-speed railway in Bilecik, so this is very important to show the Turkish tunneling industry that large machines are up to the challenge.”
Due to the challenging situations, that can be encountered along the track, the large diameter XRE has a number of unique aspects. The large diameter design enables both a screw conveyor and belt conveyor to remain in place, enabling swift conversion between modes, and operation in 100% EPB and hard rock modes.
In EPB mode, the screw conveyor acts as in any common EPB machine. The screw features a replaceable inner liner and replaceable carbide wear bits for abrasion protection. A 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.
The mixing bars and initial portion of the screw conveyor can be optionally retracted, when converting to hard rock mode. EPB knife bits are then changed with disc cutters on the cutterhead, and the EPB scrapers on the cutterhead are replaced with bucket lips. For allowing the muck to fall into the muck chute, muck paddles are installed in the cutterhead. 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. For a continuative production rates in both modes, the Robbins Torque-Shift System is used: a two-speed gearbox that enables efficient tunneling in hard, mixed, or soft ground.
While the Eşme-Salihli Railway Tunnel is segment of the Ankara-İzmir High Speed Railway Project for the Turkish State Railways (TCDD), the line, that is 508 km (316 mi) length, will finally link Polatlı in Ankara Province with Izmir, the third most populous city in Turkey, surpassing the Istanbul-Ankara High-Speed Railway as the longest rail line in the country once complete. The main purpose of this double-track railway system is to reduce a 6.5 hours’ journey to a 3.5 hours’ journey, by transporting passengers at top speeds of 250 km/h (160 mph).
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