Numerical simulation of rock fragmentation process induced by two TBM cutters and cutter spacing optimization

TBM performance depends on the rock breakage efficiency induced by TBM cutterhead. The rock breakage process is the interaction process between TBM and rock mass, which is affected by the TBM specifications, such as cutter thrust force, cutter tip width and profile, cutter spacing, revolution per minute, and torque, and rock mass properties mainly including rock material strength, rock brittleness index, joint spacing and orientation. In this study, rock chipping process induced by two TBM cutters was performed using the discrete element method (DEM). The chipping process is composed of formation of crushed zone, cracks initiation and propagation, side cracks coalescence and chip formation. The influence of the difference cutter spacing on the penetration process was also simulated by setting up a series of two dimensional UDEC models. The optimum cutter spacing on the Bukit Timah granite found in Singapore was identified to be about 100 mm provided the critical cutter thrust force can be reached.