LAUSR

Longwall mining leaves pillars and irregular blocks of coal behind in its aftermath. In this study, a shortwall block mining (SBM) technique for recovering these coal resources has been proposed. A mechanical analysis model for calculating the heights of the water-conducting fracture zone (HWFZ) in overlying strata of SBM was established based on the theory of beams on elastic foundations. Using this model and the data acquired from a working face in the experimental area, a height of 50.30 m was calculated for HWFZ corresponding to this working face. This observation indicates that the equation for predicting HWFZ in working faces specified by the Hydrogeological Procedures for Mines (HPM) standard is not suitable for application in SBM. For this reason, the Universal Distinct Element Code (UDEC) modeling program was used to analyze the developmental behavior of the water-conducting fracture zone under various determining factors in SBM. The UDEC simulations indicated that the HWFZ increase linearly with an increase in mining height, decrease linearly with an increase in the width of the protective coal pillars, and increase logarithmically with block length. A nonlinear regression analysis of HWFZ was performed using the SPSS software suite, from which a model for predicting HWFZ in SBM was constructed. This model predicted that the HWFZ was 52.58 m in the experimental area, while field measurements yielded HWFZ values varying from 47.98 to 50.06 m, which was basically consistent with the results of the prediction model and the mechanical model, thus confirming the accuracy of the mechanical model and the reliability of the regression model. The results of this study will provide critical practical references for the enhancement of coal recovery rates in mining areas and enhance theories on aquifer protection during mining operations.