The first tunnel boring machine in the world designed to quickly switch between boring and blasting excavation — nicknamed Xianglong — has rolled off an assembly line in eastern China.
A joint collaboration between the China Railway Science and Industry Group and Tsinghua University, the 230-foot TBM was manufactured in Wuhan and combines traditional tunnel boring with a drill-and-blasting technique, according to a translated press release from the Hubei Provincial Government. Designed for “complex geological tunnels,” the Xianglong offers a digging diameter of 14.8 feet, a central cutterhead diameter of 3.9 feet and weighs roughly 400 tons.
The new “boring and blasting machine” offers a unique hollow cutterhead design and uses the tandem operation of the hollow and central cutter heads to switch between three modes of operation, roughly translated as: front blasting followed by digging, front digging followed by blasting and full-face tunneling.
This allows the TBM to combine “advanced drilling and blasting pretreatment and mechanized continuous excavation,” according to the Hubei Provincial Government.
The TBM also offers retractable side cutters for adjusting the excavation cross-section and improved in-tunnel relocation, according to Global Times. An adaptive telescopic tail can adjust to various segment specifications for variable-diameter lining assembly in rock burst and large-deformation sections.
Powered byThe manufacturer also added explosion-proof shield buffers to protect the machine and a dual independent belt conveyor system to more excavated material.
A researcher at the National Key Laboratory of Hydrosphere Science and Hydraulic Engineering at Tsinghua University Qin Pengxiang was quoted in the original press release saying the new machine solves a construction bottleneck in China. Qin says that, unlike traditional tunnel boring machines, it won’t jam when encountering rock bursts, fractured zones and large deformations in soft rock.
"The two mainstream methods each have their advantages but are difficult to reconcile, hindering the high-quality development of the industry," says Qin. "Tests show that, under ultra-hard rock geological conditions, tunnel boring machines can improve tunneling efficiency by 30% after pre-splitting treatment."
The new TBM is destined to work on projects in China involving water conservancy, hydropower, transportation arteries and deep earth resource development.
Some information in this article comes from Google translations of material originally written in Mandarin.
