Numerical Estimation of Suitable Gob-Side Filling Wall Width in a Highly Gassy Longwall Mining Panel

Abstract

Determining a suitable width of gob-side filling wall (GFW) is a major concern in the application of gob-side entry retaining (GER) technology in highly gassy coal mines. This paper presents a workflow for GFW width design based on a rigorous numerical modeling analysis. A meticulously validated numerical model was built to analyze the vertical stress, entry convergence, and plastic zone distribution across the GFW with various sizes. In order to ensure the reliability of the numerical model, a strain-softening model for GFW modeling and a double-yield model for gob modeling were implemented, and the relevant input parameters’ calibration was clearly illustrated. The results demonstrated that when the GFW’s width is 2.5 m, it possesses sufficient load-bearing capacity, and the entry convergence variation tends to stabilize. Consequently, the rational GFW width was estimated as 2.5 m. The field monitoring results demonstrate that a gob-side entry, with a 2.5-m-wide GFW, meets the cross section requirement for gas drainage. The proposed design workflow and modeling procedure can potentially be applied to other GER design under similar geological conditions.