Cracking of granitic rock by high frequency-high voltage-alternating current actuation of piezoelectric properties of quartz mineral: 3D numerical study

This paper presents a numerical study on cracking of granitic rock by high frequency-high voltage-alternating current actuation (HF-HV-AC) of piezoelectric properties of Quartz mineral. For this end, a numerical method based on 3D embedded discontinuity finite elements for rock fracture and an explicit time stepping scheme to solve the coupled piezoelectro-mechanical problem is developed. Rock heterogeneity and anisotropy are accounted for at the mineral mesotructure level. Novel numerical simulations demonstrate that disc-shaped and cylindrical granitic rock specimens (with the tensile strength of about 8 MPa) can be cracked by a sinusoidal excitation with an amplitude of ~10 kV at a frequency matching one of the resonance frequencies of the specimen (e.g. 125 kHz in the present case of 30 mm radius and 10 mm height). The effects of specimen shape and electrode locations are tested. Various Quartz grain alignment schemes are tested and even the worst case of having a 50%:50% mixture of right- and left-handed Quartz crystals without any preferred orientation show stresses of about 1 MPa at the resonance frequency. The simulation results suggest that HF-HV-AC piezoelectric excitation of Quartz bearing rocks could be a potential pre-treatment technique in comminution.