Numerical Simulation of Cracking Behavior of Precracked Rock under Mechanical-Hydraulic Loading

Abstract

The cracking behavior of precracked rocks under mechanical-hydraulic loading is of great significance in underground openings or petroleum engineering. In this study, an advanced in-house finite element code PANDAS proved to be effective in simulating coupled fracturing processes under complex geological conditions was used to simulate the cracking propagation of the precracked rocks under mechanical loading and mechanical-hydraulic loading with different strength parameters. The simulation results demonstrated that (1) the cracks initiate by the induced stresses, and multiple types of tensile cracks originate from the preexisting flaws; (2) crack propagation patterns under mechanical-hydraulic loading were studied with different strength parameters, and the multiple patterns of pure tensile, main tensile, tensile-shear, main shear, and pure shear were observed; and (3) the timing of hydraulic loading has a significant impact on the fracturing process: when hydraulic loading was carried out in the phase of main crack propagation, the tensile fracture was promoted and the shear fracture was inhibited; when hydraulic loading was carried out in the phase of shear crack propagation, the shear fracture and tensile fracture were stimulated. The numerical simulation results are in good agreement with the experimental results by previous studies. The research on the cracking behavior of precracked rocks under mechanical and hydraulic loading will expand the application prospect in the fields of coal seam gas reservoir and tunnel water inrush.