Abstract: On the basis of the formulae for the Lugeon value, the shortage of Lugeon as a quantitative indicator of rock permeability in water pressure test is analyzed. By deducing the calculation formula of permeability coefficient with steady flow and unsteady flow in homogeneous postulation water pressure test, we believe that the accuracy of calculation result is higher in the presence of unsteady flow. Moreover, with Jinping-I hydropower station as an example, we calculated the permeability coefficient respectively in steady flow and unsteady flow conditions based on the measured water pressure test data of the grouting inspection drilling. The results demonstrate that the permeability coefficient in unsteady flow condition is less than that in steady flow condition in short duration water pressure test.

Key words: water pressure test, homogeneous aquifer, steady flow, unsteady flow, permeability coefficient