Mechanism and Prevention of Coal and Gas Outburst and Impact Ground Pressure Coupling Disasters in High Stress Extra - Thick Coal Seams: A Case Study
Using the Weijiadi coal mine as a case study, this paper analyzes the stress-gas coupling mechanisms driving coal and gas outburst and rock burst disasters in high-stress extra-thick seams and validates a four-in-one prevention system that effectively reduces gas emissions and concentration through integrated gas pre-drainage and water injection.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Deep beneath the earth's surface, coal mines face a unique and terrifying double threat. On one hand, the immense weight of the rock above creates a crushing pressure that can suddenly snap the coal and rock apart, sending a violent shockwave through the tunnel. On the other hand, natural gas trapped within the coal pores can build up enough pressure to explode, blasting chunks of coal and rock into the air with lethal force. When these two dangers happen at the same time, they do not just add up; they feed off each other. The crushing pressure makes it harder for the gas to escape, trapping it until it is ready to burst, while the trapped gas weakens the coal, making it easier for the rock pressure to shatter it. This deadly combination, known as a coupled disaster, turns deep mining into a high-stakes gamble where the ground can fail without warning.
Researchers from Liaoning Technical University in China have turned their attention to a specific mine, the Weijiadi coal mine, to understand exactly how this double danger builds up and how it might be stopped. They focused on a section of the mine called the East 1100 working face, where the coal seam is unusually thick and the pressure from the surrounding rock is extreme. By combining real-world measurements taken inside the mine with powerful computer simulations, the team mapped out the invisible forces at play. They discovered that the pressure in this area is not just heavy; it is dominated by horizontal forces pushing from the sides, reaching a maximum of nearly 40 megapascals. This is significantly higher than the weight of the rock column directly above, creating a field of stress that is primed for disaster.
As the mining machines moved forward, the researchers watched how the stress shifted. They found that the coal left behind between the mined area and the untouched rock, known as a coal pillar, acted like a sponge absorbing the weight. As the mining face advanced, the pressure on this pillar grew steadily. When the mining reached its final stopping point, the stress on the pillar skyrocketed to nearly 60 megapascals, a concentration factor more than four times the normal pressure. This buildup was not uniform; the side of the tunnel closest to the empty space left by previous mining became the most dangerous zone, where the pressure peaked at nearly four times the original rock stress. This extreme compression squeezed the coal so tightly that it became a perfect trap for gas, creating the ideal conditions for a sudden, violent release.
The study also revealed how the geology of the mine itself acts as a trigger. The East 1100 face sits near a large fault line, a crack in the earth's crust where rock layers have shifted. The researchers found that as the mining face approached this fault, the stress did not just rise; it jumped. The fault zone superimposed its own pressure on top of the mining pressure, causing the peak stress to increase by nearly double in some areas. This geological feature also changed how the coal reacted. The team measured two key warning signs: the amount of coal dust produced when drilling a small hole and how quickly gas escaped from that hole. They found that as the stress increased, both of these indicators rose sharply, following a predictable pattern. This confirmed that the fault was not just a passive feature but an active amplifier of the danger, turning a risky area into a critical one.
To combat this, the team tested a comprehensive safety strategy that combined four different methods into a single system. First, they drilled a series of fan-shaped holes ahead of the mining face to suck out the trapped gas before the miners ever arrived. Second, they injected water into the coal seam under steady pressure. This water did not just wet the coal; it softened it and created tiny channels for the gas to escape slowly and safely, rather than building up to an explosive point. They also installed a network of sensors to monitor the stress in the rock and the radiation emitted by the coal, providing a real-time warning system. Finally, they used electromagnetic sensors to detect any sudden changes in the rock's electrical properties that might signal an impending failure.
The results of this combined approach were clear. After implementing these measures, the amount of gas released from the working face dropped by 32 percent. More importantly, the concentration of gas in the upper corners of the tunnel, a critical spot where gas tends to accumulate, stayed well below the dangerous limit of 1.0 percent. The warning indicators for coal dust and gas desorption remained at safe levels, even as the mining face moved deeper into the high-pressure zone. The study suggests that by understanding the specific way stress and gas interact in these thick coal seams, and by using a multi-layered defense system, it is possible to tame these coupled disasters. The work provides a practical blueprint for keeping miners safe in some of the most challenging and dangerous environments on Earth, proving that even when the ground is under immense pressure, careful science can keep the balance.
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