In December 2025, in an engineering triumph, CRCHI’s Beishan #1 – a large gradient spiral hard rock TBM – completed the advance of a formidable 7.1km spiral incline at Mazong Mountain, Gansu, China.
This monumental feat marked the breakthrough of the access tunnel for the China Beishan Underground Laboratory, which CRCHI said is the world’s first large slope, tight turn spiral inclined tunnel.
The achievement heralds a technological leap for China in constructing long distance, ultra hard rock tunnels featuring steep downward gradients and continuous spiral curves.
The Beishan #1 TBM boasts a 7m excavation diameter and integrates an advanced autonomous system with one touch activation, surrounding rock prediction, automated tunnelling, real time deviation correction, re-gripping automation, self adapting parameters, and seamless manual automatic switching.
It masters tunnelling on a 10 per cent downward slope while navigating horizontal curves of just 255m radius.
By overcoming the critical challenges of automatic steering correction and flawless mode transition, the TBM achieves fully unmanned excavation under uniform geology – maintaining attitude deviations within ±50 mm.
This breakthrough not only sets a new benchmark but establishes China as a leader of autonomous tunnelling technology worldwide.
Designated a National Key Project, the China Beishan Underground Laboratory is engineered around a sophisticated ‘one spiral ramp, two horizontal drifts, and three vertical shafts’ configuration.
The ramp’s bold three-dimensional helix – with a relentless -10 per cent gradient and a remarkably tight 255m horizontal turning radius – traverses granodiorite of exceptional integrity and strength.
With rock classifications predominantly at Class I to II, quartz content of 25–30 per cent, and uniaxial compressive strength peaking at 260 MPa (averaging 170 MPa), this ranks among the world’s most formidable tunnelling environments.
The dual challenges of sustained excavation through intact, ultra-hard rock while navigating continuous downhill tight curves demanded nothing short of revolutionary engineering and equipment performance.
Rising to this challenge, CRCHI’s R&D team conquered a series of pioneering technologies: advanced cutterhead systems for extreme hard rock fragmentation, artificial joint-assisted rock-breaking methods, a compact, short shield body engineered for sharp curves, a fully automated guidance system, and a high-capacity continuous conveyor for spoil removal on steep helical paths.
Their mastery is embodied in the bespoke Beishan #1 TBM – a machine conceived, designed and built entirely through CRCHI innovation.
Completing the factory acceptance test in Changsha City in September 2022 and transported over 3000km to site, the Beishan #1 commenced its advance on 1 January 2023. In the face of relentless, monolithic hard rock, it set outstanding advance records – 21.6m in a single day and 342m in one month – while achieving fully automated operation throughout the demanding downhill spiral sections.
The TBM deftly negotiated all seven tight 255m radius curves and eight straight-line segments, culminating on 26 December 2025 in the breakthrough of the full 7km advance.
The success of Beishan #1 does more than validate China’s proprietary technology for high-gradient spiral tunnelling – it also demonstrates CRCHI’s prowess in global underground engineering in both heavy equipment manufacturing and complex subterranean construction.
For more information, contact tangzhongwu@crchi.com