In order to study the influence of roof stress and fracture distribution characteristics on the stability of stope surrounding rock under repeated mining in close-distance coal seams, the research background of this paper is the close-distance coal seam mining of a mine in Guizhou province, China. The dynamic evolution characteristics of stope roof caving and the stress environment change law under repeated mining are studied by using the method of similar simulation experiment, numerical simulation, and field verification. The results show that the roof stage under repeated mining can be divided into four stages: normal mining, roof deterioration, end face roof leaks, and support crushing. The tip-to-face distance, support height, and support working condition are the main influencing factors in end face roof control. The main reason for the support crushing is that the roof above the support is broken, the main roof cannot form the self-stable structure, and the support force is insufficient. The roof dynamic load is high, and the subsidence of the end face roof is large, which is prone to roof caving during the stope roof weighting. Moreover, the roof weighting is frequent under repeated mining, which leads to the broken roof and the support cannot be supported, resulting in the occurrence of the support crushing accident. The control strategies for stope roof under repeated mining are provided based on the thorough study findings. The working face 17101 roof is successfully controlled by the aforesaid procedures, which provides the foundation for the management of stope surrounding rock under repeated loading.

In order to effectively solve the problem of gas concentration overrun in the upper corner of goaf and tailentry during the mining of panel 9303 in Anshun Coal Mine, based on the advantages of controllable trajectory and wide coverage area of directional drilling technology, high directional long boreholes are arranged in tailentry 9303 to extract pressure relief gas. Firstly, the principle of high directional long borehole drainage technology is introduced, and the fracture evolution of overlying strata is obtained through using numerical simulation, theoretical calculation, and field practice, and the fracture evolution range is determined to be 6–12.69 m, and rationality of fracture height obtained by theoretical analysis and numerical simulation is verified by the method of field borehole peep observation. Through the analysis, it is concluded that the best location of the final hole is within the range of 6–12.69 m of the roof of coal seam 9#. The field practice has proved that the final hole position of the high directional long borehole is arranged at 12 m from the roof of coal seam 9#, and the average gas extraction concentration can reach 40%–50% after the borehole enters the stable extraction stage, the purity of gas extraction is up to 8.5 m³/min, and the gas concentration in the upper corner of panel 9303 is stable below 0.5% during mining, which achieves good gas drainage and control effect and provides a new way for gas control under similar geological conditions.

Coal wall spalling characteristics and stability control mechanisms in steeply inclined coal seam (SICS) mining are more complex and dynamic due to the imbalanced mechanical constraint environment of the coal wall. This study investigates the characteristics of coal wall spalling in SICS mining using field measurements, theoretical analysis, and numerical simulations. The internal relationship between coal wall spalling and different influencing factors is also established, and the corresponding coal wall stability control measures are put forward. Results indicate that the primary form of coal wall spalling is wedge-shaped. Under the combined action of roof pressure and gravity, the wedge body produces two components along the dip and strike directions, forming two structural planes, a and b. The a-plane predominantly experiences shear slip failure, while the b-plane primarily undergoes tensile failure. The failure criteria for the a-plane and b-plane of the wedge body are determined, with mining height, coal strength, roof pressure, and coal seam dip angle being the main influencing factors in SICS mining. The stability relationship of the coal wall under various advancing distances is investigated using the 3DEC numerical simulation. The majority of coal wall spalling occurs as an asymmetric wedge body, and the relationship between different influencing factors and coal wall spalling is examined. A comprehensive preventive and control technique for coal wall spalling in SICS mining is proposed. The engineering application demonstrates positive results and provides theoretical and technical guidance for the prevention and control of coal wall spalling in SICS mining.