Numerical study on mechanical response and fracture characteristics of deep marble under intermittent disturbance

Engineering disturbance, especially intermittent disturbance caused by blasting or drilling, significantly influences the mechanical properties of rocks. In this study, a series of particle flow simulations were conducted using the Parallel-Bond model to investigate the effect of intermittent loads on the disturbance response of marble at depth (deep marble for short), with a focus on its mechanical behavior, failure mechanism, acoustic emission (AE) and energy evolution characteristics. The results indicate that under intermittent disturbance load, there are inflection points and stress plateaus in the stress-strain curves. As the maximum principal stress σ₁ and disturbance amplitude A_d increase, the stress plateaus are elongated, indicating that the plastic deformation in the σ₁ direction increases. The disturbance effect exhibits the complex interaction between initial strengthening mechanism (such as "dynamic confining pressure effect") and subsequent weakening mechanism. The initial strengthening mechanism is dominant at lower A_d, while the weakening mechanism is gradually enhanced with the increase of A_d. The marble shows a mixed failure mode of tension-shear under different σ₁ and A_d conditions. However, as the intermediate principal stress σ₂ increases, the failure mode transitions from tension-shear mixed failure to shear failure. In the disturbance stage, AE events increase with the increase of σ₁ and decrease with the increase of σ₂. In addition, the fluctuation range of pre-peak strain energy increases with the increase of σ₂. The dissipation energy of the rock specimen increases gradually and accelerates at higher A_d.