摘要
Based on Robin′s concept of effective pressure and Bernabé′s permeability-isograms(k-isos) characteristics in pore fluid pressure(pp) and confining pressure(pc) figure,a new method for calculating the non-linear effective pressure(the secant effective pressure) is developed.Meanwhile,the new method and Bernabé′ method for calculating tangent effective pressure were used for analyzing the data of 12 samples in the present and previous researches.Two kinds of effective pressures were calculated.The results reveal that just as k-iso is linear,the secant effective pressure is equivalent to the tangent effective pressure.Otherwise,the two kinds of effective pressure laws are not the same.Moreover,it is found that the points describing the relationship between permeability k and the secant effective pressures are less scattered than the ones between permeability k and the tangent effective pressures.To assess the validity of the new method,two kinds of curves between permeability and effective pressures were fitted by power function and exponential function respectively,and it is observed that the secant effective pressures present the better fitting results than those done by the tangent effective pressures,suggesting a more feasible way of effective pressure calculation.