In October 2021, 13.77 m (45.18 ft) Robbins XRE tunnel boring machine (TBM) set world records for fastest boring by day, week and month at the Esme-Salihli Railway Tunnel in Turkey. The machine set records of a best day of 32.4 m (106 ft), a best week of 178.2 m (584.6 ft), and a best month of 721.8 m (2,368 ft). Launched in March 2021, the machine bored 3.05 km (1.90 miles) on the Esme-Salihli Railway Tunnel as part of the Ankara-?zmir High Speed Railway Project for the TCDD.

“When the strength, force and torque generated by our Crossover TBM are taken into account, we consider it to be a beast. It has performed extremely well in this tunnel,” said Onur Kansu, TBM Manager for project contractor Kolin Construction. He added “We are proud we have accomplished such high performance.”

The machine began its bore in altered gneiss, then passed through mélange consisting of gneiss, sandstone, claystone, mudstone, quartz, and silt. By the end of the bore the machine was excavating in mainly mudstone. Core drillings were taken every 200 m (656 ft) prior to boring so the crew felt confident with the geology—just one of several factors that contributed to the record rates. “A proper geological analysis, choosing the right TBM, a professional crew and a contractor who believes that they can break records are all key,” said Kansu. “Scheduled maintenance periods, an expert team, availability of sufficient spare parts, and good logistics also made it possible for us to reach our targeted advance rates.”

The project is particularly important for the Turkish tunneling industry, showing what is possible at larger TBM diameters. “We have disproved the idea that it is difficult to reach high advance rates while boring in EPB mode with large diameter TBMs. Crossover TBMs enable us to find quick solutions in changing ground, so we believe they will be the preference for future projects,” said Kansu.

With tunnel excavation finished, work will continue on the 508 km (316 mile) line that will connect Polatl? in Ankara Province to Izmir, the third most populous city in Turkey. Once complete, the Ankara-?zmir High Speed Railway will be the longest rail line in the country, conveying passengers at top speeds of 250 km/h (160 mph) in a railway journey of about 3.5 hours.