Key Takeaways & Executive Findings
- •• Gas-driven tensile failure is the dominant mechanism in coal and gas outbursts, and its influence is amplified by the uncovering coal area. • Increasing uncovering coal area leads to higher gas emission volumes, larger outburst hole deflection angles, greater roof displacement, and larger damage zones. • Tensile failure criterion predicts coal failure regions that largely coincide with mixed failure criterion, but far exceed those predicted by shear failure criterion. • A progressive cyclical method of coal uncovering was developed, providing a novel approach for safe coal mining.
Abstract
Deep mining is imperative, and the consequent coal and gas outburst disasters triggered during coal uncovering are becoming increasingly severe. Therefore, this study investigated the mechanical mechanisms of outburst instability from three dimensions: experiment, numerical simulation, and field application. Based on physical simulation tests with different outburst pore diameter, it was found that the gas pressure relief rate, gas emission volume, and outburst dynamic phenomena increase with outburst pore diameter. The migration patterns of the gas-solid two-phase flow evolved over time approximately into suspension flow, plug flow, dune flow, and stratified flow. The dominant influence of gas-driven tensile failure was amplified by uncovering coal area. The employment of the ''fluid-solid-damage'' coupling model revealed that coal damage, gas emission volume, deflection angle of outburst hole, roof displacement, maximum horizontal tensile stress, the horizontal tensile stress zone, the peak seepage force, and the damage zone all increased with uncovering coal areas. At the gas pressure of 0.74 MPa, when the uncovering coal areas were 3.189, 4.754 and 6.225 m, the total gas emission volumes were 4.72×10−4, 16.83×10−4, and 17.67 m2/s, deflection angles of outburst hole were 150.79°, 152.89° and 158.66°, the maximum roof displacements were 0.044, 0.046, and 0.325 m, and the peak seepage force were 0.85, 1.27, and 1.46 MPa/m, respectively. The regions of coal failure calculated by tensile failure criterion largely coincided with those calculated by the mixed failure criterion, far greater than those calculated by the shear failure criterion. As the increase of uncovering coal area, tensile weights of 80.72%, 89.78%, and 93.01%, respectively. Comparisons with field outburst cases showed that both gas emission volume and outburst hole deflection angle reflected the tensile failure of coal. The mechanical instability process of outbursts under the influence of uncovering coal area and gas pressure was analyzed, developing the progressive cyclical method of coal uncovering, which provided a novel approach for the achievement of safe coal mining.
1. Introduction
Coal, possessing both energy and resource attributes, remains an irreplaceable component in national strategic development [1]. Although coal mine safety has improved in recent years, challenges such as the ''three highs and one disturbance'' (high in-situ stress, high gas pressure, high ground temperature, and mining-induced disturbance) associated with deep mining continue to cause outburst incidents [2,3]. Coal and gas outburst involving the progressive failure and instability of coal body, resulting in the ejected coal carried by high-pressure gas into the excavation space, is the catastrophic dynamic hazard occurring during underground coal mining [4,5].
Critically, outbursts triggered by coal uncovering through rock cross-cuts are significantly more severe [6]. Due to the tensile failure induced by high-pressure gas, the intensity of outbursts during cross-cut uncovering coal is typically more than six times greater than those occurring in other types of roadways [7]. Furthermore, over 80% of exceptionally large outbursts occur specifically during coal uncovering [8]. Therefore, research into the mechanisms of coal failure and instability during coal uncovering is of paramount importance for ensuring safe and efficient deep mining.
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LI Yunfu, ZHANG Chaolin, LI Bobo, WANG Enyuan, CHEN Jiawei, YANG Xianhe, LI Chong (2025). Tensile failure mechanism enhanced by uncovering coal area during coal and gas outburst. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.10.008
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the main finding of this study on coal and gas outbursts?
The study reveals that gas-driven tensile failure is the dominant mechanism in coal and gas outbursts, and its influence is amplified by the uncovering coal area. Larger uncovering coal areas lead to more severe outbursts with increased gas emission, larger deflection angles, and greater damage.
How does the uncovering coal area affect the outburst intensity?
As the uncovering coal area increases, the gas pressure relief rate, gas emission volume, and outburst dynamic phenomena all increase. For example, at a gas pressure of 0.74 MPa, increasing the uncovering coal area from 3.189 m to 6.225 m resulted in a significant rise in total gas emission volume and roof displacement.
What methods were used in this research?
The research employed a combination of physical simulation tests, numerical simulations using a 'fluid-solid-damage' coupling model, and field application comparisons to investigate the mechanical mechanisms of outburst instability.
What is the significance of the tensile failure criterion in predicting outbursts?
The tensile failure criterion was found to predict coal failure regions that largely coincide with those from a mixed failure criterion, but far exceed those predicted by shear failure criterion. This indicates that tensile failure is a critical factor in outburst mechanisms.
What practical approach was developed for safe coal mining?
A progressive cyclical method of coal uncovering was developed based on the analysis of mechanical instability processes, providing a novel approach to mitigate outburst risks and achieve safe coal mining.
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