Influence Mechanism of Main Roof Height on Surrounding Rock Stability of Gob-Side Entry Driving

The main roof directly affects the stress environment and the control effect of the surrounding rock of gob-side entry driving. A mechanical model of the surrounding rock of gob-side entry driving was established to analyze the influence mechanism of different main roof heights on the surrounding rock stability of the roadway under similar geological conditions. In addition, the influences of the main roof heights on the stress distribution of the surrounding rock were qualitatively analyzed. A quantitative analysis of the stress and deformation distribution characteristics of the surrounding rock were conducted by Universal Distinct Element Code (UDEC) when the heights were 0, 5, and 10 m based on the actual geological conditions. Results show that waste rocks in the caving zone and damaged immediate roof could provide four different stress combinations to key rock block, which is affected by the main roof height and other related parameters. With the increase in the main roof height, the hinged stress between the key rock blocks and the plastic damage area of the physical coal wall are reduced, the damage range of immediate roof gradually increases, and the vertical stress of narrow coal pillars first increases to 5.22 MPa and then remains at approximately 1.92 MPa. Therefore, the supporting strength of roof and the physical coal wall should be enhanced. Research results are successfully applied in the Yanjiahe Coal Mine. The conclusions provide significant theoretical guidance for controlling surrounding rock stability of the roadway under similar conditions.