Meikuang Anquan (Jan 2024)
Study on the influence of negative pressure on seepage characteristics of broken coal bodies with different pore perimeters
Abstract
In order to investigate the influence of negative pressure on the gas seepage characteristics in crushed coal, a self-designed negative pressure pumping simulation permeability test system was used to study the gas seepage law in different grades of crushed coal under the influence of negative pressure. The sensitivity of gas energy loss and apparent permeability in this process to the influence of negative pressure was analyzed. The results show that: with the increase of negative pressure, the non Darcy effect of gas permeability under the same pore structure is more prominent than the Darcy effect. However, with the increase of Talbol grading coefficient n, the internal pores increase, and the boundary between the two becomes blurred, and the correlation coefficient begins to approach. By introducing an inertia turbulence correction coefficient to characterize the energy loss of gas under different pore structures, the overall trend decreases with the increase of n. δ is in an unstable stage when n is between 0.2 and 0.6, and after n>0.6, the numerical value δ is basically stable, that is, as the pore structure increases, the energy loss of gas seepage decreases, tending towards Darcy seepage; when the negative pressure is less than 60 kPa, there is a significant difference in the changes in the negative pressure sensitivity curves of samples with different gradations. However, when the negative pressure is greater than 60 kPa, the curves close to each other, and the larger the n value is, the lower the deviation of the negative pressure sensitivity curve is. That is, when the negative pressure is smaller, the apparent permeability is more susceptible to negative pressure. The permeability of fractured coal bodies around holes is easily affected by their pore structure when the negative pressure of extraction is low. In terms of pore structure and extraction negative pressure, non Darcy seepage often appears, causing problems such as poor extraction and affecting extraction efficiency.
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