Study on key strata and surface deformation prediction for overburden separation grouting mining in adjacent panel based on foundation beam theory

With the intensive exploitation of coal resources, the phenomenon of surface deformation becomes more prominent. This issue has directly threatened the safety of surface building structures and the regional ecological balance. Based on the elastic foundation beam theory, we investigated the deformation characteristics of key strata under overburden separation grouting in adjacent panel mining and predicted surface deformation. By establishing a mechanical model of key strata in single panel and adjacent panel mining, we solved the deflection curves of key strata using the initial parameter method. Combined with UDEC numerical simulation, we determined the foundation coefficient of each section, and fitted its quantitative relationship with injection-production ratio(IPR) and panel width. By integrating the probability integral method with equivalent mining height theory, a surface deformation prediction model was constructed. The results showed that the maximum subsidence of the key strata decreased quadratically as the IPR increased and increased quadratically as the panel width increased. The unequal widths of adjacent panels cause asymmetric subsidence of the key strata; however, such deformation can be effectively mitigated by maintaining the IPR within a reasonable range. The field validation in Panel 3119 reveals a deviation of only 6.38% between the predicted maximum surface subsidence (251.8 mm) and the measured value (236.7 mm), confirming the high reliability of the prediction model. This study offers theoretical insights into key strata control and surface deformation prediction.