Abstract
In the study described in this paper, a general particle dynamics (GPD) code was developed to simulate rock fragmentation by tunnel-boring machine (TBM) cutters in mixed-face ground. In the GPD code, a novel algorithm of the contacts at the boundary between two different media was proposed. The mechanism of rock fragmentation by two disc cutters and the effects of cutter spacing on rock fragmentation in mixed conditions were investigated. With increasing cutter spacing, the propagation pattern of Hertzian cracks varied and an optimal cutter spacing was found. The mechanism of rock fragmentation by a disc cutter and a drag bit and the effects of the acting position of different TBM cutters on rock fragmentation in mixed conditions were studied. The optimal acting position of the disc cutter and the drag bit was found to benefit the effectiveness of TBM rock fragmentation.
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