Abstract: The selection of particles’ parameters is of vital importance to simulate rock cutting by the tunnel boring machine(TBM）. The parallel bond shear/tensile strengths between particles, in particular, their ratio is one of the key controlling parameter, which directly determines the ductility or brittleness of the specimen and influences the process and the cutting result. In order to explore the effects of ductility brittleness on rock cutting, this paper conducts the following researches: (1) Creating 9 numerical models by applying different parallel bond strength ratios, and simulating uniaxial compression test and Brazilian tensile test respectively so as to examine the macromechanical behavior and failure mode of every model with different ductility-brittleness. (2) Making double-cutter rock cutting simulation on the nine models above, and monitoring every model’s crack propagation and cutter force condition. (3) To reduce the impact of randomness on the simulation results, making five repetitive simulations for every model by changing random seeds and analyzing the computation of five results comprehensively. Through these simulation researches above, it is discovered that as the ratio of shear bond strength to tensile bond strength( ) grows, brittleness increases and the failure mode of rock samples changes gradually from shear failure to brittle tension failure; and the crushed zone of cutter rock breakage reduces and the tension cracks are more likely to extend between cutters, thereby producing larger bulks of rock pieces. As the brittleness of the model increases, the normalized specific energy decreases and the efficiency of the rock cutting increases. With the same bond strength radio, by applying different random numbers, the specific failure condition of every model is somewhat different; but the overall failure mode is comparable.

Key words: tunnel boring machine (TBM), particle flow code, rock cutting, ductility-brittleness, parallel bond strength