Integrative solution of stress evolution in overburden roof strata during the coal seam mining by application of complex variable functions methodology

Large-scale roof collapse is a major dynamic hazard threatening the safe coal mine operations. Understanding the deformation and failure characteristics of overburden rock strata, as well as deciphering the stress evolution mechanism of overburden rock structure in mining stopes, is of great theoretical advancement and engineering applications in roof disasters prevention. This study employs a theoretical derivation to systematically analyze the characteristics of overburden roof deformation and caving behavior during the coal seam mining. By modeling the trapezoidal caving zone in the overburden roof strata as a complex functional system, the stress distribution within the caving zone and adjacent intact strata was mathematically characterized. Stress evolution patterns of overburden strata at different caving stages were derived under both elastic and elastoplastic deformation conditions, accompanied by the demarcation of elastic-plastic zones. In addition, the critical length for the first caving and periodic caving of overburden are theoretically determined. To validate the proposed analytical framework, comprehensive numerical simulation and physical model tests are conducted to investigate the overburden roof caving characteristics during coal seam mining. Quantitative comparisons between experimental, numerical results and theoretical analyses were performed in terms of the caving range of roof strata, the critical length for the roof strata caving and stress distribution. The consistencies among different approaches confirms the reliability of the theoretical model, providing a robust foundation for optimizing mining designs and implementing effective roof control strategies. • The stress distribution characteristics of the entire mining stope were derived employing the complex variable functions methodology. • Stress evolution patterns of overburden strata at different caving stages were derived under both elastic and elastoplastic deformation conditions. • Proposed a mechanical discriminant condition for overburden caving, and theoretically determined critical lengths for the first and periodic caving employing complex variable functions. • According to the solution of complex variable functions theory, the criterion of overburden caving was established in numerical simulation.