The vertically-jointed coal seam, especially after water drainage, is easy to lead to large-area coal wall spalling (CWS). To alleviate the problem, a strut subjected to equivalent central-concentrated force was proposed for elaborating critical conditions for coal instability based on CWS characteristics, determining the main control factors. The sensitivity analysis of factors driving CWS revealed that the coal between 3.3 and 4.56 m was the most vulnerable. A microblasting technique was proposed for controlling CWS by increasing the friction coefficient at the weakened-primary coal interface, improving the coal stress, and reducing the equivalent mining height. The paper presented the application of universal distinct element code models to simulate the CWS mechanism with different joint mechanical parameters and microblasting heights. The reduction of spalling intensity indicates that the microblasting weakening of the upper part coal could improve the overall stability of the coal. LS-DYNA is employed for simulating the fractures development between blasting holes, and the rationality of optimized blasting parameters is revealed. The fracture characteristics of the observation hole in field demonstrated that the hole was effectively fractured by microblasting. The spalling parameters including depth, width and frequency were obviously reduced, which showed the rationality in microexplosion controlling spalling.

Previously conducted studies have established that the sudden collapse of large areas of overhanging roofs in longwall working faces can cause shock loads and wind blast. In order to solve the problem of the hard and stable roof (HSR) being difficult to collapse in the initial mining stage, a combination of theoretical analysis and numerical simulation is used, taking Dongqu coal mine as the engineering background. The mechanical model of the initial fracture of the main roof is established, the relationship between the thickness-to-span ratio of main roof, the internal stress of the roof is analyzed, and the relationship between the thickness of the roof and the initial weighting step is revealed. The method of hydraulic fracturing (HF) is proposed to pre-crack the main roof in order to achieve controllability of the roof. The effect of HF on the control of the HSR is analyzed. The main conclusions are as follows: under the condition of a certain span of the rock beam, a smaller thickness of the rock beam makes for a larger tensile stress inside of it, increasing the likelihood that the rock beam will fracture. It is possible to reduce the initial weighting interval of the main roof by decreasing the thickness of the HSR and increasing the thickness of the load layer. The abutment pressure in the initial mining stage is obviously reduced after HF. The technical scheme of HF was proposed and applied in the field, and the field observations show that after HF, the HSR can collapse in time at the initial mining stage, leading to remarkable results being achieved.

The mining confrontation caused by a super-long working face is an important factor that leads to difficulties in the control of surrounding rock in facing-mining roadways. To address this issue, this study takes the 18106 working face of Xiegou Coal Mine as the engineering background. First, deformation characteristics of the surrounding rock in two stages of roadway mining are explored, and the principle of determining the time for fracturing construction is presented. Additionally, the influence of fracturing space position on the control effect of the roadway’s surrounding rock is examined. Results show that the roadway which is influenced by adjacent working face mining has obvious asymmetric deformation, and the order of deformation is as follows: pillar side > roof > coal side > floor. The roof activity in goaf is the key factor of roadway deformation, and the proportion of deformation is 60%, followed by the influence of advance stress, accounting for 38%. After fracturing, with the increase in fracturing height, the deformation of the surrounding rock decreases, and the decrease in deformation of the roof and two sides also reduces, while the decrease in deformation of the floor remains relatively stable. The reasonable fracturing height is 10 m, and the reasonable fracturing construction time is 17 days before the confrontation between the working face and the roadway. Field practice suggests that there are effective cracks in the roof after fracturing, and the deformation of the surrounding rock in facing-mining roadways is reduced by more than 60% compared to that without fracturing. Hydraulic fracturing is significant for controlling the deformation of the surrounding rock in facing-mining roadways.