Abstract
Borehole pressure relief technology is an effective way to reduce the elastic energy in the surrounding rock of deep roadways, thereby reducing the risk of regional rock bursts. To avoid large deformation of the roadway caused by pressure relief holes with large diameters and insufficient pressure relief with small pore diameters, this study proposes precise pressure relief holes with nonequal diameters in order to achieve strong pressure relief with minimal disturbance based on the abutment pressure distribution pattern. To verify the pressure relief effect of the nonequal diameter holes, numerical simulations were performed in FLAC3D. This study investigated stress field, deformation laws, and plastic failure zone of roadway surrounding rock with 100 mm pressure relief holes, nonequal diameter precision pressure relief hole (100 mm + 300 mm), and 300 mm pressure relief holes. The simulation results show that, as the diameter of the pressure relief hole increases, the coupling effect of evenly spaced adjacent pressure relief holes is strengthened, thus improving the pressure relief efficiency. When pressure relief holes of nonequal diameter are adopted, the stress environment of the surrounding rock is clearly improved compared to100 mm pressure relief holes, and the plastic failure range increased by 2-3 times. The roof-to-floor convergence with nonequal diameter is 30.8% that of 300 mm pressure relief holes and 41% that of 100 mm pressure relief holes. Furthermore, the rib displacement is 30.4% and 46.9% that of 300 mm and 100 mm pressure relief holes, respectively. Thus, precise pressure relief holes with nonequal diameter provide both strong pressure relief associated with large diameter holes and small disturbance of small diameter of small holes. This study provides a reference for precise pressure relief application with pressure relief holes.
Highlights
Deep mining fundamentally changes the behavior and engineering responses of coal and rock masses due to the action of high ground stress, high ground temperature, high osmotic pressure, and strong time effect for a long time [1,2,3]
If the borehole diameter is too small and the hole spacing is too large, the expected pressure relief effect is not achieved whereas if the aperture is too large and the spacing is too small, instability and failure of roadway surrounding rock will eventually occur. erefore, this study proposes a precise pressure relief holes with nonequal diameters based on the distribution pattern of abutment pressure to achieve the desired effects of small disturbance and precise and strong pressure relief in surrounding rock of the roadway. e proposed pressure relief hole provides a reference for application of precise pressure relief with pressure relief hole
Existing borehole pressure relief theory and the internal and external stress field theory were used to investigate the effect of pressure relief hole diameter on the pressure relief effect
Summary
Deep mining fundamentally changes the behavior and engineering responses of coal and rock masses due to the action of high ground stress, high ground temperature, high osmotic pressure, and strong time effect for a long time [1,2,3]. Lan et al [17] simulated and analyzed the effect of borehole diameter, borehole spacing, and coal stress on pressure relief [18] Both Ma et al [19] and Song et al [20] studied the combined support mechanism of combined support of roadway pressure relief holes and bolts. If the borehole diameter is too small and the hole spacing is too large, the expected pressure relief effect is not achieved whereas if the aperture is too large and the spacing is too small, instability and failure of roadway surrounding rock will eventually occur. Erefore, this study proposes a precise pressure relief holes with nonequal diameters based on the distribution pattern of abutment pressure to achieve the desired effects of small disturbance and precise and strong pressure relief in surrounding rock of the roadway. If the borehole diameter is too small and the hole spacing is too large, the expected pressure relief effect is not achieved whereas if the aperture is too large and the spacing is too small, instability and failure of roadway surrounding rock will eventually occur. erefore, this study proposes a precise pressure relief holes with nonequal diameters based on the distribution pattern of abutment pressure to achieve the desired effects of small disturbance and precise and strong pressure relief in surrounding rock of the roadway. e proposed pressure relief hole provides a reference for application of precise pressure relief with pressure relief hole
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