Coal bed methane drainage is the main approach to lower
risks of
coal seam while raising the efficiency in natural resource utilization.
The negative pressure used for extraction in coal mines is largely
determined empirically due to a lack of experimental research on how
coal permeability changes under the combined influence of effective
stress and negative pressure. This results in low gas extraction efficiency
and concentration. In this paper, to study the effect law of complex
stress and extraction on coal permeability during coal and gas co-mining,
a test system was specially designed to determine the gas flow and
coal permeability of coal samples under different stress paths and
negative pressure conditions in the lab. The study analyzed the correlation
between coal permeability, effective stress, and negative pressure
and subsequently developed a permeability evolution model for gas-bearing
coal under negative pressure conditions. The results showed that the
permeability of coal increases with the increase in negative pressure
and decreases with the increase in effective stress; the permeability
of coal can be abruptly changed by changes in stress loading patterns;
the established model of permeability evolution of gas-bearing coal
can better reflect the correlation between permeability, effective
stress, and negative pressure. The research outcomes offer a valuable
theoretical foundation for the efficient extraction and utilization
of methane in coal mines.
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