Permeability-strain equation relation to complete stress-strain path of coal sample

With the Electro-hydraulic Servocont rolled Rock Mechanics Testing System,the permeability of soft coal sample related to complete stress-strain path is experimented with instantaneous permeating method of data auto control.An annular strain sensor is set up firstly in testing,and the curves,reflecting the relationship between permeability of coal sample and principal stress difference,axial strain and volumetric strain,as well as the relevant equations are established.Thus it can be seen the coal sample permeability coefficient is twofold function of volumetric strain.It is binomial equation when the sample volume decreased,and five-polynomial one when the volume increased.The equation can be applied to the numerical analysis of the coupled stress field and the fluid flow field,and the calculated results agree well with those observed.