Repeated mining of dual coal seams will reactivate the stable rock layers caused by mining of a single coal seam,exacerbating the impact of deformation and damage.Therefore,it is of great significance to study the laws of overlying rock strata movement caused by repeated mining of coal seams.Based on the influence function method-key stratum(IFM-KS)model,a rock strata movement calculation model suitable for multi-layer mining conditions was proposed,revealing the movement and deformation laws of rock strata after secondary disturbance due to repeated coal seam mining.The accuracy of the new model for predicting rock movement in dual coal seam mining was verified by theoretical calculation and numerical simulation with UDEC.The results of theoreti-cal calculation of rock displacement had the same trend as those of numerical simulation,with an average error rate of about 15％.Based on the calculation results of the rock movement model and the porosity of the interlayer and overlying strata,compared with single-layer coal mining,the porosity of the goaf caused by the mining of dual coal seams changes sharply,and the rock damage tends to be more severe.The upper and lower goaf can be connected through cracks forming air leakage channels.This calculation model can provide certain guidance for prediction of rock deformation and analysis for the distribution of porosity in goaf areas under similar mining conditions.
strata movementkey stratuminfluence function methodrepeated mining
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