Largest tunneling machine of its kind completed

A new hard-rock tunnel boring machine rolled off the production line on Sunday in Changsha, Hunan province. [Photo provided to]

A tunnel-boring machine with a diameter of more than 7 meters rolled off the production line on Sunday in Changsha, Hunan province.

Produced by China Railway Construction Heavy Industry Corp and China Railway 18th Bureau Group Corp, the machine is about 100-meter-long. It can achieve a horizontal turning radius of 200 meters, and a vertical curve radius of 380 meters of tunneling.

As the first large-slope tunnel-boring machine in the world, the so-called Beishan No 1 will be used in the construction of an underground laboratory to research disposal technologies for high-level radioactive waste in Beishan, Gansu province.

The machine will excavate a spiral curve slope in Beishan, about 7.2 kilometers long. With each 10 meters of excavation, the working height of the machine will drop 1 meter.

The landscape in Beishan consists mainly of granite, a type of hard rock, making work more challenging, said Xu Chunxian, head of the Beishan construction team from China Railway 18th Bureau Group Corp.

The design of the cutting head of Beishan No 1 has a rock breaking efficiency three times that of a machine with a traditional plane cutter head, said Wu Min, vice-president of the TBM design institute of China Railway.

The design team improved the space structure of the machine, coupled with advanced guidance, direction control and an automatic cruising system to assist driving and increase the flexibility of the machine in cutting large-slope spirals.