Design of the Appropriate Width of the Filling Body for Gob-side Entry Retaining in Hard and Thick Top Coal with Gangue Concrete

The roadway support and goaf treatment under the condition of hard and thick roof are key challenges in the coal mining process. The gob-side entry retaining technology provides a new solution. This paper takes the 15311-working face of the 1890 Coal Mine of Xinjiang Jiao Coal Group as the engineering background to conduct research on the design of the reasonable width of the coal-gangue concrete filling body for gob-side entry retaining. By establishing a mechanical action model of gob-side entry retaining, the support resistance of the coal-gangue concrete is calculated to be 14266.96kN, and the bearing capacity of the 1.2-m-wide filling body is theoretically checked. The outcomes demonstrate that it complies with the support requirements. By means of FLAC3D software, numerical models featuring different widths were constructed for analysis. It is thus concluded that the entry-retaining with a 1.2-m-wide filling body exhibits high overall stability and low deformation. Field practice shows that during the entry-retaining period, the overall deformation of the roadway is small, the integrity of the surrounding rock is good, and the entry-retaining effect is satisfactory. Finally, the reasonable width of the coal-gangue concrete filling body in the 15311-working face is determined to be 1.2m. The research findings can serve as a reference for designing the filling body width under analogous geological conditions.