Microscale Characterization of Fracture Growth in Increasingly Jointed Rock Samples

• Published in: Rock mechanics and rock engineering Vol. 55; no. 10; pp. 6033 - 6061
• Main Authors: Gao, Ge, Meguid, Mohamed A.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.10.2022; Springer Nature B.V
• Subjects: Acoustic emission; Acoustic propagation; Anisotropy; Civil Engineering; Clustering; Confining; Contact force; Crack propagation; Deformability; Deformation; Discrete element method; Distribution; Earth and Environmental Science; Earth Sciences; Evolution; Failure analysis; Failure mechanisms; Failure modes; Formability; Fracture mechanics; Frequency dependence; Geophysics/Geodesy; Growth; Jointed rock; Laboratories; Mechanical analysis; Mechanical properties; Microstructure; Original Paper; Pressure; Rock; Rock masses; Rocks; Sediment samples; Shear; Spatial distribution; Statistical methods; Stress-strain relationships; Joint intensity; Rock mass behavior; Increased confinement; Acoustic emission information; Microstructure evolution
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-022-02965-x

Discrete element method (DEM) is employed to investigate the fracture growth and failure mechanism of increasingly jointed rock samples subjected to increasing confinements. Synthetic rock mass models are developed on the basis of joint configurations created within laboratory samples, and the micromechanical parameters of the DEM are calibrated to replicate the mechanical response measured in the laboratory. Subsequently, the effects of increasing the level of initial joint frequency and confining pressure on the strength, deformability, stress–strain relationship, and failure mode transition of the rock samples are analyzed. At the microscopic scale the tensile and shear crack distributions, fragmentation characteristics, AE frequency–magnitude statistics and spatial clustering of source locations are examined to shed light on the mechanical behavior and deformability of jointed rock mass. Results show that the distribution of the magnitude of AE events is prone to decay as power law in tandem with the spatial distribution of the source locations that exhibit a fractal character. Noteworthy is the decrease of seismic b values associated with failure pattern from axial splitting to shear fracture upon increase in confining pressure, which is indicative of an accelerating number of events of increased magnitudes. Finally, the microscopic evolution of the fabric and force anisotropy as well as the characteristics of spatial distribution of contact forces provide micromechanical insights into the macroscopic behavior of jointed rock samples upon the rise in confining pressure. Highlights This study addresses an important problem related to the initiation, evolution and propagation of failure in jointed rock mass using discrete element method Acoustic emission is employed to shed some light on the mechanical behavior and deformability of jointed rock mass Microscale characterization of fracture growth mechanism of jointed rock samples are achieved by examination of the microstructure and stress transmission