Prediction of relative displacement for entry roof with weak plane under the effect of mining abutment stress

In coal mining, the entry roof with a weak plane (ERWP) is vulnerable to large relative displacement, and even caving influenced by the mining stress from the adjacent working face (AWF) for underground mining engineering. A typical field case in a chinese coal mine demonstrates that the mining abutment stress can strengthen the relative displacement along the weak plane for the entry roof. To address this conditions, a method to improve the width to height ratio (W/H) of the coal pillar to reduce the effect of the mining stress on the stability of the ERWP based on a numerical model is proposed. In order to improve the reliability of the numerical model, the double-yield model for the gob material, the Mohr-Coulomb model for the pillar material, and the interface element for the weak plane were validated in detail. The results of the validated model indicate that the relative displacement induced by the mining abutment stress is divided into four stages, and it decreases significantly as the W/H increases. In the final, the W/H more than 8 is determined to reduce the effect of the mining abutment stress on the ERWP. The modelling procedure can be repeated and is necessary in other geological and engineering conditions since the determined W/H may be another value.