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"MOST CHALLENGING PROJECT EVER" COMPLETED BY TBM
An 8m (26.2 foot) diameter Robbins Main Beam TBM has broken through at China’s Yin Han Ji Wei project. The machine overcame 17.5km (10.9 miles) of tunnel in some of the most difficult geology ever encountered, breaking through in the first quarter of 2022. The water diversion tunnel traverses the Qinling Mountains of Shaanxi Province, with up to 2,000m of cover.
“Every day was full of challenges. We are most proud of our teamwork and unyielding spirit,” said a representative for tunnel contractor China Railway Tunnel Group (CRTG). The ground, consisting of mainly quartzite and granite, was estimated to have a rock hardness of between 107 and 309 MPa (15,500 to 45,000 psi) UCS, with high abrasivity.
“This was in my opinion the most challenging project ever completed by TBMs, and it proves TBMs are up to overcoming even the most difficult conditions. I have great respect for the CRTG crews and management, and I thank them for moving TBM technology to a new level,” said Robbins President Lok Home.
During tunnelling, crews encountered over 14,000 rock bursts, some with energy as high as 4,080kJ. Rock bursting was controlled using steel slats in conjunction with the McNally crown support system, while zones of stress were predicted using a micro-seismic monitoring system.
The micro-seismic system records rock stresses in a borehole 20m (65 feet) ahead of the face and predicts the potential for rock bursting following comparative analysis with similar data from other projects, as well as from nearby sections of tunnel. iC