Multi-physical field coupling model for thermal evolution analysis in coal mine goaf: a numerical investigation

Spontaneous coal combustion in goaf areas represents one of the most severe thermodynamic hazards in coal mining operations, characterized by its concealment, complex air leakage patterns, and challenging control measures. The accurate localization of high-temperature zones is crucial for mitigating potential spontaneous combustion risks. Unlike previous studies that focus primarily on hazardous area delineation, this study establishes a novel multi-physical field coupling model incorporating temperature, pressure, and gas concentration fields, with defined source terms for oxygen consumption and coal oxidation heat release, to evaluate the position and migration of high-temperature zones. The dynamic mesh technique is innovatively employed to simulate the temporal evolution of temperature fields during actual mining processes. A sensitivity analysis investigates the influence of key control factors, including face advance rate, ventilation volume, and residual coal thickness, on spontaneous combustion risks. Results indicate that increased ventilation flow leads to higher temperatures in high-temperature zones and greater distances from the working face; accelerating face advance rate effectively suppresses spontaneous combustion; while increased residual coal thickness causes high-temperature zones to migrate toward the working face. Based on these relationships, a multivariate function model is developed to predict the location of high-temperature zones with high accuracy. This predictive model provides theoretical guidance for mitigating spontaneous combustion hazards in goaf areas.