Stress environment around head entries with pillarless gobside entry retaining through numerical simulation incorporating the two type of filling wall

Longwall mining is the most productive system for underground extraction of coal. Many coal mines use a pillarless mining. Reserving a gateroad for the usage of next panel mining is a popular gob-side entry retaining. Thus, the conventional entry retaining method requires an installation of filling walls. The mechanical properties of filling materials largely determine the quality of job-side entry retaining. Stress field evolution study around head entries when main roof console length increase with two variants of filling wall. Ansys code was used to analyze the stress evolution law under different mining conditions. As a result of numerical simulation, it was found that in the case of gob-side entry retaining, the localization of maximum stresses in surrounding rock is determined by the length console of the main roof, which hanging on the border with the gob, and the filling walls deformation module. Potential location of roof cutting, stress gradient and extremum stress in the main roof define the stability of entries. Main roof console length and filling material parameters control can help to the formation of a stable structure around the entry to meet the requirements of the next working face.