Beishan Underground Laboratory Spiral Access Tunnel

CRCHI engineered the bespoke Beishan #1, a large-gradient spiral hard-rock TBM, for the access tunnel into the China Beishan Underground Laboratory in Gansu, a National Key Project sited inside Mazong Mountain. The 7-metre diameter machine completed a 7.1-kilometre spiral incline, descending on a sustained -10% gradient through granodiorite of Class I to II integrity with uniaxial compressive strength peaking at 260 MPa. Negotiating seven 255-metre radius horizontal curves under fully unmanned excavation, the TBM held attitude deviations within 50 millimetres before breakthrough on 26 December 2025.