In order to prevent the multi-dynamic disasters induced by rock burst and roof water inrush in strong rock burst coal seams under multi-aquifers, such as is the case with the 207 working face in the Tingnan coal mine considered in this study, the exhibited characteristics of two types of dynamic disasters, namely rock burst and water inrush, were analyzed. Based on the lithology and predicted caving height of the roof, the contradiction between rock burst and water inrush was analyzed. In light of these analyses, an integrated method, roof pre-splitting at a high position and shattering at a low position, was proposed. According to the results of numerical modelling, pre-crack blasting at higher rock layers enables a cantilever roof cave in time, thereby reducing the risk of rock burst, and pre-crack blasting at underlying rock layers helps increase the crushing degree of the rock, which is beneficial for decreasing the caving height of rock layers above goaf, thereby preventing the occurrence of water inrush. Finally, the proposed method was applied in an engineering case, and the effectiveness of this method for prevention and control of multi-dynamics disasters was evaluated by field observations of the caving height of rock layers and micro-seismic monitoring. As a result, the proposed method works well integrally to prevent and control rock burst and water inrush.

Promoting the ability of anti-bursting of the confining rock of a coal roadway is of significant importance to the safe production of a coal mine. In particular, in deep-buried coal mines, highly frequent rock burst occurs due to large earth pressure and complex geological conditions, which needs serious improvement. This paper investigated a type of confining rock modified method, which can modify the physical properties of the surrounding rock and form a crack region and a reinforced region by blasting and grouting reinforcement. Based on a set of physical model experiments and numerical modeling, the results of a comparative analysis between a normal roadway and the modified roadway in the static stress redistribution, dynamic stress, damage evolution, and energy dissipation suggest that the modified confining rock is capable of protecting the coal roadway against rock burst from roof stratum, obviously reducing and transferring the concentered static–dynamic stress out of the cracked region, dissipating the dynamic energy by plastic damage in the cracked region, and keeping the integrity of the reinforced region. In addition, the velocity of the dynamic stress vibration wave at the surface of the modified coal roadway is obviously reduced, which is beneficial for decreasing the movement of cracked rock blocks and protecting the lives and goods in the coal roadway.

Addressing the insufficient pressure relief in the deep coal mass and the deterioration of the surrounding rock bearing structure due to increased borehole diameter in conventional borehole pressure relief techniques, a static expansive fracturing method for pressure relief in coal seam boreholes is proposed. A critical stress model for static expansive fracturing in coal seam boreholes is established through theoretical analysis, and numerical simulations are conducted to compare and analyze the differences between this method and conventional borehole pressure relief techniques in terms of roadway pressure relief effect and surrounding rock stability control. The results indicate that using a 150 mm borehole with a 75MPa expansive stress achieves a comparable state of full pressure relief in the rib coal as a 250 mm borehole, while increasing the pressure relief range in the deep coal mass by a factor of approximately 3.6. Although conventional borehole pressure relief methods can enhance pressure relief by increasing the borehole diameter, they significantly expand the plastic zone in the shallow surrounding rock, aggravating surrounding rock deformation. In contrast, the static expansive fracturing method for pressure relief in coal seam boreholes actively directs fractures in the deep high-stress coal mass, promoting the expansion and interconnection of its plastic zone to form a deep structural weakening zone, while markedly reducing the disturbance and damage to the shallow surrounding rock. This method breaks through the limitations of passive borehole expansion for pressure relief, offering dual advantages of efficient deep pressure relief and shallow surrounding rock stability protection, and providing a new approach for rockburst prevention.

To investigate the evolution of floor rockburst instability tendency and optimize borehole pressure-relief horizons in roadways with retained bottom coal, theoretical analysis and numerical simulation were employed to investigate the effects of bottom coal thickness on composite-floor stability, load-bearing and energy-storage states, and borehole pressure-relief response. Based on the equivalent transformed-section method, a stability analysis model for the bottom coal–floor composite structure was established to reveal the mechanism by which increasing bottom coal thickness reduces structural stability and influences the floor instability tendency. Numerical results show that, with increasing bottom coal thickness, the dominant load-bearing and energy-storage response progressively shifts from the floor strata to the bottom coal–floor composite structure and then to thick bottom coal. An energy–stress index K was introduced to characterize the transition in the load-bearing and energy-storage states of the composite floor. Further analysis of the effect of borehole vertical depth indicates that pressure-relief effectiveness depends on the spatial matching between the weakened zone and the main load-bearing and energy-storage zones, rather than on indiscriminately increasing borehole depth. Under the simulated conditions, the reasonable borehole vertical depth ranges from 3.0 to 4.0 m for a bottom coal thickness of 2 m and from 4.0 to 5.0 m for bottom coal thicknesses of 4, 6, and 8 m. The results provide a theoretical reference for understanding the relative evolution of floor rockburst instability tendency and optimizing borehole pressure-relief horizons in roadways with retained bottom coal.