Abstract: To rationally select cutters for tunnel boring machines(TBMs) in extremelyhard rocks to improve the TBM construction efficiency and reduce cutter consumption, a case study is conducted on the YE project in Xinjiang, China. Under the condition of intact Class Ⅱ tuff with a uniaxial compressive strength of 100－150 MPa, the excavation performance of narrow and conventional cutters is tested and compared, and the feasibility and rationality of reducing the width of the disc cutter ring to improve the degree of TBM penetration and excavation speed are explored. The results reveal the following: (1) Narrow cutters can considerably improve the penetration degree and construction speed, which becomes more obvious when increasing the compressive strength of the surrounding rock. (2) The consumption of narrow cutters is higher than that of conventional cutters, while the proportion of failure forms of these two cutter types remains almost the same, with minimal impact on the utilization rate of TBM operations. (3) The narrow cutters exhibit a superior economic benefit over conventional cutters.

Key words: hard rock tunnel boring machine, disc cutter, cutter ring width, penetration degree, advance rate, cutter consumption