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URUMQI, Feb. 9 (Xinhua) -- After checking the machine parameters, Bai Junlin pressed the "on" button in the control cabin of a tunnel boring machine (TBM) named "Tianshan."

Fifty-eight disc cutters mounted in the machine's cutter head started to work immediately, rolling over and chipping away the rocks.

The giant machine, 285 meters long and weighing almost 2,000 tonnes, was moving forward in the Tianshan Shengli tunnel. Located in northwest China's Xinjiang Uygur Autonomous Region, it is the country's longest expressway tunnel under construction.

"It's much easier to drill a tunnel with the TBM, which can achieve a top daily advance of 40 to 50 meters, four times faster than that of traditional drilling and blasting," said Bai, who will stay at the construction site during the upcoming Spring Festival with his 300-plus colleagues, in a bid to complete the construction task as scheduled.

Stretching for 22 km, the tunnel is also a crucial part of the 1,300-km expressway linking Urumqi, capital of Xinjiang, with Yuli County, 50-km south of the city of Korla in central Xinjiang.

The construction of the tunnel, at an altitude of 3,200 meters in the Tianshan Mountains, faces severe climate and geological challenges.

To deal with the problems, Tianhe Mechanical Equipment Manufacturing Co., Ltd., located in the eastern province of Jiangsu, produced two tailored TBMs named "Tianshan" and "Shengli."

Yet, the TBMs are so huge and heavy that they could barely be delivered as a whole to the construction site in Xinjiang, which is more than 3,000 km away from Jiangsu.

"Each drilling machine was dismantled into 352 accessories. It took a month and more than 100 trucks to transport the parts," said Yin Huabin, assistant manager of the TBM operation team working at the tunnel's north section.

Highly automated, environmentally friendly and suitable for complex conditions, the two drilling machines currently working at both ends of the tunnel have greatly reduced manpower and improved efficiency.

"The two giant machines have drilled about 300 meters in 40 days, and can do better if tuned properly," said Yin.

The construction of the tunnel, launched in 2020, is expected to be completed in 2025. The Urumqi-Yuli expressway will then become an arterial road connecting northern and southern Xinjiang and shorten the travel time from Urumqi to Korla from seven hours to three hours.