The rock cutting simulation of heterogeneous granite using FDEM method

Many advanced rock breaking methods are emerged form improving the ROP in deep formation drilling in recent years, such as electric pulse rock breaking, ultrasonic rock breaking and hydraulic rock breaking. However, the traditional mechanical rock breaking is still the mainstream rock-breaking method. A detailed understanding of the rock cutting mechanism is essential to achieve high efficiency in rock breaking and to optimize the cutting parameters. This study establishes the simulation model of heterogeneous granite cut by polycrystalline diamond compact (PDC) cutter using FDEM, and the friction work factor is put forward to characterize the friction work proportion of PDC cutter in cutting process. Analysis is done on the variations in friction work factor, force, and failure mechanism of granite under different cutting depths. The results show that the three-dimensional force increase gradually with the increase of cutting depth. When the cutting depth is shallow, the tensile (Type I) failure is dominated, ductile failure mainly occurs to granite and the size of chips is small. When the cutting depth is deep, the proportion of tensile failure is low, the internal shear crack of granite gradually dominates, the failure mode of granite gradually changes to brittle failure, the chips gradually become larger. Friction work factor and failure factor can visualize the change of friction energy consumption of PDC cutter in rock cutting and the failure mode of rock. This study leads to an enhanced understanding of rock breaking mechanisms in rock cutting, and provides the basis to improve the PDC bit design.