TBM Cutting Performance in Hard and Abrasive Granite in Hong Kong
Tunnel Boring Machine (TBM) tunnelling projects in hard and abrasive rock pose different challenges compared with those in soft ground. One of the challenges is the determination of penetration rate of tunnelling and the design of TBM cutter with respect to anticipated ground condition. There is little published information on slurry TBM performance in granitic rock. Two 7.45m dia. slurry TBMs (Uptrack and Downtrack) have been driven through granitic rock, mixed ground and completely decomposed granite for MTRC SCL Contract 1103 in Hong Kong. The paper focuses and discusses in detail the cutting performance of 7.45m diameter slurry shield TBM in the granitic rock part of the tunnel, based on the Colorado School of Mines method. Discussions also include how the performance in Downtrack and Uptrack tunnel was influenced by the modification in the machine, as well as the abrasivity and the observed cutter life. A TBM gathers a massive amount of information during tunnelling. A detailed knowledge of the interaction of the ground conditions with the TBM parameters will serve as useful reference for the design of TBMs and prediction of performance.