Analysis of the Mechanism of Main Effects of Microscopic Parameters on Macroscopic Parameters in the PFC2D Parallel Bonding Model

To establish a quantitative mapping relationship between macro- and micro-parameters in the PFC2D parallel bonding model, and in view of the inherent complexity of the mutual validation process between laboratory experiments and parameter calibration, this paper takes uniaxial compression tests as the mechanical reference. By combining orthogonal experimental design, Pearson correlation analysis and multivariate analysis of variance, this study systematically investigates the effects of 10 micro-parameters on 6 macro-mechanical indicators (modulus of elasticity E, Poisson’s ratio ν, uniaxial compressive strength σc, friction-to-cohesion ratio FCR, crack initiation strength σci and crack damage stress σcd). To reduce the coupling dimension between cohesion and internal friction angle in the calibration of PFC macro–micro parameters, this paper defines the Friction-to-Cohesion Ratio (FCR) as the ratio of the equivalent macroscopic angle of internal friction to the equivalent macroscopic cohesion, and systematically conducts sensitivity analyses of uniaxial compression simulations. The results indicate that the elastic modulus E is primarily governed by E*, E¯*, k¯* and Rf; the Poisson’s ratio ν is mainly influenced by E*, k*, E¯*, k¯* and Rf; the uniaxial compressive strength σc, the crack initiation strength σci and the crack damage stress σcd are primarily regulated by σ¯c and Rf; whilst the Friction-to-Cohesion Ratio (FCR) is mainly affected by σ¯c, φ¯, Rf, c¯ and β; Elasticity parameters and strength parameters are governed by different micro-mechanisms, reflecting the fundamental decoupling of stiffness and strength in the PFC model. This study established a progressive ‘screening–validation–quantification’ sensitivity analysis framework, revealing the directional regulation patterns of various micro-parameters on macroscopic responses, thereby providing a theoretical basis for the targeted optimisation and efficient calibration of micro-parameters in PFC discrete element simulations.