Developed by CRCHI, Beishan No. 1 broke through on the Beishan underground laboratory’s main project access ramp in December. CRCHI says the milestone on the world’s first large-gradient, small-radius spiral tunnel marks a significant technological achievement for construction equipment for long-distance, ultra-hard rock spiral tunnel projects.
The underground laboratory has one access ramp, two horizontal tunnels and three vertical shafts. The access ramp features a spatial spiral alignment with an overall comprehensive gradient of -10% and a horizontal turning radius of 255m.
The surrounding rock is predominantly granodiorite, classified as Grade Ⅰ and Ⅱ, with a quartz content of 25-30%. The uniaxial compressive strength of the rock ranges from 110 to 260MPa, with an average of 170MPa.
CRCHI says this means the project has the most intact and highest-strength rock of projects worldwide.
Beishan No.1 TBM rolled off the production line at CRCHI’s Changsha factory in September 2022 and was transported the 3,000km-long journey to the jobsite to begin excavation in December 2022.
CRCHI says under the working conditions of long-distance, ultra-intact hard rock, the TBM set impressive records with a maximum daily advance of 21.6m and a maximum monthly advance of 342m.
It realised automatic TBM excavation under the challenge of a large-gradient downhill spiral and downhill driving, and completed the construction of all seven small-radius turning sections (255m in radius) and eight straight sections.
