Optimization of disc cutter life and penetration rate in hard rock can be one of the biggest predictors of project success. With hard rock TBMs being used today in ever more difficult conditions and longer tunnels, the question of which type of disc cutter to be used becomes critical. At one such project in Northeastern China, varying disc cutter tool steels and sizes were put to the test on a total of nine different 8.5m diameter hard rock, Main Beam TBMs from various manufacturers. The TBMs excavated sections of a vast water tunnel in similar granitic geology.This paper will look at the development of 20-inch disc cutters and the case for large diameter cutters, using the most recent example in China as a focus area of study. Varying advance rates, cutter life, tool steels, and challenges excavating the rock will be discussed. The paper will conclude with recommendations for optimal cutter life in TBMs destined to bore long tunnels in hard rock.
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