Engineers at Tsinghua University, working in partnership with China Railway Group, have unveiled Xianglong, a 4.5-metre-diameter hybrid tunnelling machine designed to overcome one of the most persistent bottlenecks in underground construction: excavating through extremely hard rock formations. The machine was formally presented in Wuhan, Hubei province, and represents what its developers describe as the world’s first genuinely hybrid boring-and-blasting system.
Two Excavation Methods, One Machine
Xianglong’s core innovation lies in its dual-mode operation. The machine integrates a conventional mechanical tunnel-boring cutterhead with an automated drilling and blasting unit built directly into the same platform, allowing it to switch between, or even combine, mechanical cutting and precision blast-hole drilling without needing to withdraw from the tunnel face. This is a significant departure from standard practice in the industry, where traditional tunnel boring machines that encounter rock too hard for their cutterheads typically have to be partially disassembled and swapped for blasting equipment, a process that can halt progress for days or weeks at a time.
Efficiency Gains for Hard-Rock Tunnelling
According to its developers, the hybrid design increases tunnelling rates through hard-rock strata by up to thirty per cent compared with conventional single-mode equipment, primarily by eliminating the equipment-swap downtime that has long constrained hard-rock excavation schedules. The machine is intended for deployment in some of the most demanding tunnelling environments in China’s infrastructure pipeline: high-mountain railway tunnels, deep underground hydraulic conduit systems, and other subterranean infrastructure projects that routinely encounter unpredictable and highly variable rock conditions.
The development is being framed within China’s broader push to expand rail connectivity through some of its most geologically challenging terrain, including high-altitude and seismically active mountain regions where conventional tunnelling equipment has historically struggled with cost overruns and schedule delays caused precisely by the kind of hard-rock encounters Xianglong is designed to handle more gracefully. If the efficiency gains hold up under sustained field deployment, the machine could mark a meaningful shift in how large-scale tunnelling projects are planned and budgeted, reducing the schedule risk that hard-rock sections have traditionally introduced into major infrastructure timelines.
– Rashmi M
