Accurate characterization of the deformation–fracture mechanism and instability precursor characteristics of flawed rock masses is the core prerequisite for engineering rock mass stability evaluation and prevention-control design. To clarify deformation–fracture behaviors and failure precursor characteristics, rock-like models with different flaw lengths were fabricated using gypsum, quartz sand, and barite powder. Embedded strain cubes, digital image correlation (DIC), and acoustic emission (AE) techniques were employed to synchronously monitor deformation evolution and fracture response under uniaxial compression. Based on the tangent modulus evolution of stress–strain relationship, the deformation process was divided into initial compaction, steady-state deformation, crack propagation, and failure stages. Elastic modulus, uniaxial compressive strength, and residual strength decreased with increasing flaw length. The regulatory intensity of flaw length on the local strain deflection angle ( γ ) followed: passive-loading end > active loading end > flaw tip. Post-steady-state deformation, the models were dominated by tensile fracture events and eventually showed a tensile-dominated mixed failure mode. For small-flaw models, cumulative Benioff strain (CBS) shows accelerated pre-instability release; tensile cracks preferentially developed at flaw tips, with shear cracks propagating therefrom. CBS and relative variation of γ (|∆ γ |) exhibited a sinusoidal relationship, and their abrupt amplitude changes or phase desynchronization could be failure precursor criteria. For large-flaw models, more shear-type, high-energy, low-frequency fracture events associated with the flaw zone were generated initially, while the pre-failure CBS-|∆ γ | response plateau period could act as the instability early-warning window.
Wang et al. (Mon,) studied this question.