Experimental Research On Coal Rock Permeability Characteristics Under Multi-factor Coupling Effect

Coal rock permeability is an important index to measure the difficulty of gas drainage,and it can be used to predict gas emission.It has many applications in actual production and has been widely studied by scholars at home and abroad.The change of permeability is mainly affected by stress,temperature,gas pressure,etc.The study of permeability under the coupling of different factors has always been an important content in coal-bed methane exploitation and mine gas disaster prevention.To this end,coal rock permeability tests including stress,temperature,and gas pressure were carried out in this article,and studied its changing laws under different conditions.The t results show that under three test schemes,Helium has the highest permeability,followed by nitrogen,and methane is the lowest,.The main reason for this phenomenon is that coal has different adsorption properties for different gases,which results in different degrees of adsorption and expansion of coal under different seepage gases;Under the action of gas-solid coupling,the overall permeability is V-shaped,but the degree of change of curved surface is methane>nitrogen>helium.Under different volumetric stress levels,the permeability is an asymmetrical V-shaped curve.Affected by the confining pressure,pore pressure and diffetent seepage gas,the strength of the slippage effect varies in the test,which also causes the critical pressure to change;Under different pressure levels,the permeability is a negative exponential function curve;Under the effect of stress-heat coupling,the overall permeability of coal rock shows an L-shaped change.When the effective stress is low,the deformation effect of temperature will promote the increase of permeability.When the effective stress rises,the compression effect on the pores and cracks of coal and rock will increase rapidly,and the permeability will appear as a negative power function curve;at different temperature levels Next,the permeability is a negative exponential functionUnder the coupling effect of pore pressure and temperature,when the test conditions change to the two wings of the curved surface with high temperature and low pressure,high pressure and low temperature,the coal permeability increases,while in the middle of the curved surface,the permeability decreases.At different temperature levels,the permeability change curve is similar to the gas-solid coupling curve.The critical pressure and the degree of permeability rebound are affected by the temperature and seepage gas.Under different pore pressure levels,the permeability changes and the force The thermal coupling curves are similar and all conform to the changing law of negative power function.Figure[55]table[23]reference[72]...