199 Discretization was performed using a hybrid mesh (tetrahedral + hexahedral elements) with mesh grading. The maximum element size at the mining level was about 1.5 m, while in strata distant from the excavation horizon the mesh was progressively coarsened (up to ~35 m) to optimize computational cost while preserving accuracy in the area of interest. Figure 4 - View of lithological strata represented in the 3D numerical model (left) and Hybrid discretization of the large-scale 3D numerical model (right) Rock mass behaviour was represented using the Generalized Hoek–Brown (GHB) strength criterion combined with GSI-based quality characterization and a disturbance factor D, allowing laboratory-scale intact properties to be reduced to rock-mass-scale conditions influenced by mining-induced degradation. The rock strength parameters at the excavation level were adopted from laboratory testing of core specimens and complemented by intact-rock constants required for constitutive and failure descriptions used in the numerical modelling (e.g., the mᵢ constant in the Hoek– Brown criterion). In the workflow, a clear distinction was maintained between intact-rock properties—primarily governed by the material behaviour of the specimen—and rock-mass behaviour, which additionally reflects discontinuities, jointing, and scale effects. The intactrock input parameters representative of the excavation horizon, used as the basis for subsequent rock-mass parameter estimation and/or model calibration, are summarized in Table 1 Table 1 - Intact-rock strength and deformability parameters adopted for the excavation horizon and used as input for the analyses. Parameter Cohesion Angle of friction ∅ Poisson's ratio Density Unit MPa GPa MPa o – g/cm3 – Value 45.0 33.5 20.5 32 0.22 2.28 8 2.3. Convergence monitoring Model validation was based on underground convergence monitoring conducted using roof-to-floor telescopic convergence indicators (“convergometers”) installed at selected locations within the panel, including long-life excavations and zones influenced by the mining
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