A new study has introduced the 'percolation factor' to help identify precursors to coal and gas outbursts based on outburst percolation theory. Conducted by researchers at Liaoning Technical University, this investigation utilized uniaxial compression experiments on coal rock, monitored with computed tomography (CT) scanning, to explore the phenomenon of gas releases exceeding expected reservoir capabilities during mining operations.
The pressing concern for the coal industry is the frequent occurrence of gas and coal outbursts, particularly with increasing mining depths. This study presents the percolation factor as a quantifiable measure indicating whether the coal mass has undergone significant structural changes—specifically, whether large-scale gas migration pathways, termed "percolation transformations," have formed.
The experimentation revealed intriguing dynamics about coal's porosity and its link to gas outburst likelihood. Researchers found percolation probability and correlation length both increased with porosity, and noted major changes occurred as porosity approached the theoretical percolation threshold. According to the data, when this threshold is crossed, the probability of gas migration channels forming within the coal significantly surges, thereby elevifying the chances of outbursts.
The findings suggest serious safety applications for the coal industry. Specifically, the outburst percolation theory corresponds with evidence gathered by uniaxial compression tests, where significant internal microstructural failures were detected before any visible damage occurred on the coal exterior.
Among the main findings was the assertion: "When the porosity of the coal reaches or exceeds this threshold, the slope of the percolation probability curve increases sharply, significantly raising the likelihood of percolation." This insight establishes new parameters for monitoring coal integrity and gas release potential, especially as the mining depth progresses.
The experimental setup employed CT technology synchronized with the compression machine to provide real-time monitoring of internal changes within coal samples during stress tests. This innovation marked advances not only for predictive capacities but also for securing the safety of miners against hazardous events triggered by gas outbursts.
This innovative approach allows researchers to build quantitative relationships between porosity and percolation parameters under varying stresses, significantly contributing to the discussions around coal and gas outburst premonitory indicators. The research concludes with the idea: "The proposed percolation factor is a measure of percolation transformation in coal samples," emphasizing its potential as a key tool for the industry.
Overall, the findings highlight the importance of developing effective monitoring systems and safety precautions for preventing gas outbursts, ensuring the long-term viability of coal as part of alternative energy strategies.