Coupled TM‑damage modeling and global sensitivity analysis of thermal spalling in heterogeneous rocks

Thermal spalling in heterogeneous rocks under rapid heating poses critical risks to deep mining and geothermal operations. In this study, we develop a coupled thermal–mechanical–damage (TM‑D) model that explicitly incorporates Weibull‑distributed heterogeneity to a single fracture in rock, and validate it against ceramic quenching and granite acoustic emission experiments. Distance‑based generalized sensitivity analysis (DGSA) is applied to quantify the influence and interactions of key parameters, revealing the dominant controls on spalling onset, severity, and damage morphology. The results demonstrate that thermal stress dominates crack initiation and propagation, that lateral constraints can significantly delay and suppress spalling, and that material heterogeneity markedly influences peak stress and damage modes within a certain range of thermal expansion coefficient and has multiple effects on thermal spalling. This study provides a theoretical basis for quantitative assessment and parameter optimization of thermal spalling processes in rock masses.