Study On Impact And Permeability Characteristics Of Anisotropic Coal

Most of the coal seams in China belong to low-permeability coal seams.In the process of mining,gas extraction is an important factor affecting the mining progress.Because the coal seam is heterogeneous and anisotropic,the permeability in different directions is different.So there are a large number of scholars have studied the permeability of coal seam,but for the impact after the different directions of coal seam permeability change rules are rarely reported,based on this,this article through self-control system of vertical impact device bedding direction for different coal samples with different strength,obtain the dynamic stress of coal and rock under different impact strength change rule,and then,on the impact strength under different coal sample of the TC-? multilayer superposition,permeability testing device of joint development of gas reservoir simulation and establish the coal and rock anisotropy permeability calculation model,obtained the permeability of coal and rock under different impact strength distribution.The main conclusions are as follows:(1)The stress-strain variation law of coal samples in different bedding directions under different impact strengths shows great differences.When the strain rate is similar,the maximum average peak stress of vertical bedding is the largest,the maximum average peak stress of parallel bedding is the second,and the maximum average peak stress of oblique bedding 45° is the smallest.(2)Under the same confining pressure and axial pressure,the permeability of raw coal samples in different bedding directions decreased exponentially with the increase of inlet pressure.However,the permeability of coal samples in different bedding directions increased exponentially with the increase of inlet pressure after impact.At the same pressure,coal samples in different bedding directions have the highest permeability parallel to bedding direction and the lowest permeability perpendicular to bedding direction before and after the impact.After impact,the permeability of coal samples in three directions increases exponentially with the increase of impact,and the permeability of coal samples parallel to the bedding direction is the largest.(3)Through the calculation of permeability calculation model,it is determined that the permeability of coal sample in any direction decreases gradually with the increase of gas pressure before the coal sample is impacted.Under the same confining pressure and axial pressure,the permeability of coal samples in any direction increases with the increase of impulse.Under the same impulse,with the increase of gas pressure,the permeability of coal samples in any direction increases gradually.