Particle flow numerical simulation study on fracture nucleation in red sandstone considering initial nonlinear deformation

Abstract

This study systematically explores the evolution of microcracks and localized nucleation characteristics in red sandstone under uniaxial compression using Particle Flow Code (PFC) integrated with innovative numerical simulation techniques. To address the inherent nonlinear deformation behaviour of rock during initial loading stages, a novel dual-stage modulus matching parameter calibration method was proposed. This method effectively reproduces the complete stress–strain process of red sandstone under uniaxial loading. Furthermore, the acoustic emission (AE) characterization technique in PFC was enhanced through optimizing spatiotemporal clustering criteria and localization algorithms for microcracks. The rationality of this approach was validated by analysing AE energy characteristics and the correlation between microcracks and macroscopic fractures. To accurately identify the spatial distribution and threshold stress of microcrack nucleation, a full-field synergistic strain calculation method and local strain concentration coefficient (LSCC) for PFC based on digital image correlation (DIC) were proposed. The results demonstrate that strain information exhibits higher sensitivity compared to fracture information, and the LSCC effectively identifies threshold stresses corresponding to microcrack nucleation and rock failure. The novel PFC methodologies proposed in this study advance numerical simulation techniques and offer valuable insights into the evolution, nucleation, and failure mechanisms of microcracks in rocks.