Abstract: Large-diameter shield tunneling in hard rock strata has low tunneling efficiency and high cutter consumption. To address these issues, a central triple-disc cutter excavation scheme is proposed, and 16-inch triple-disc cutters with three typical cutter profiles (trapezoidal, round, and flat edges) are selected for rock-breaking tests under extreme working conditions. Using a tunnel boring machine excavation modal comprehensive test platform, hard-rock shield tunneling is simulated to test key parameters, including cutterhead disc cutting parameters, cutter shaft bearing force, starting torque, multispeed running-in vibration characteristics, and rock debris characteristics under extreme loads, thus analyzing cutter performance and rock-breaking effect. The results show the following: (1) Under different penetration conditions, the cutterhead thrust and torque of trapezoidal-edge cutters are greater than those of round-edge and flat-edge cutters, and trapezoidal-edge cutters require the highest rock-breaking energy. (2) Starting torque at the single-edge end is generally more stable than that at the double-edge end, and the torque change at the double-edge end exceeds 30% for some cutters. (3) The double-edge end is the main stress area during excavation, with stresses 10%－25% higher than those at the single-edge end. Among the three cutter profiles, the trapezoidal edge bears the greatest force, whereas the round cutting edge bears the smallest stress. (4) The structural stability of the cutters differs considerably. The vibration running-in test shows that some cutters have initial assembly defects, whereas others have internal damage under extreme loads. (5) Triple-disc cutters with all three cutter profiles effectively break hard rock, and flat-edged cutters produce the lowest central rock ridge.

Key words: shield tunnel, triple-disc cutter, cutter profile, cutter test, hard rock tunneling, ultimate load