Abstract: From the perspective of microstructure of rocks, based on reasonably simplifying the actual tunneling condition, and by employing particle flow code (PFC2D), two-dimensional numerical simulation of rock fragmentation of shield machine cutters is put forward. The mechanism of rock fragmentation under the situation of sequential cutting by two shield cutters is studied; its influential factors and corresponding experiments are carried out to verify the mechanical properties of rock fragmentation. Studies show that: first, it is the cutter's tip that is of the most destructive effect; second, the force of cutters fluctuates constantly along with the cutting process; and the horizontal cutting force is greater than the vertical cutting force; third, it is different between the single-pole cutting and sequential cutting since in the process of sequential cutting, the former cutter leaves many residual cracks, which decrease the cutting force of the following cutter; forth, from the aspect of cutting performance, rock cracks become bigger and cutting force become greater as cutters go deeper; so we can conclude that the cutting depth and the cutting force are closely related; last, the experimental situation of the accumulation of cracks and chips at the front of cutters and the wave phenomenon of cutting force in the experiment show great agreement with the results of numerical simulation.

Key words: shield machine, cutter, sequential action, rock fragmentation, particle flow code, numerical simulation