[S-CG43] Environment formed and maintained by active faults

[SCG43-P04] Effect of pore pressure oscillation on hydraulic conductivity of fractured rocks -an experimental study-

*Yang Li¹, Shogo Kawakita³, Daisuke Asahina², Takato Takemura⁴ (1.Nihon University Integrated Basic Sciences, 2.Geological Survey of Japan AIST, 3.Nihon University College of Science and Technology , 4.Nihon University College of Humanities and Sciences)

Keywords:Hydraulic conductivity, Laboratory experiment, Pore pressure vibration

Earthquakes change pore pressure and hydraulic conductivity of aquifers, and these changes affect each other. For example, for faults in the aquifer, pore pressure oscillations move the particles on the surface of the fault and increase the hydraulic conductivity of the fault. In this study, we experimentally investigated the effect of pore pressure oscillation on the hydraulic conductivity of fractured Kimachi sandstone under different confining pressure conditions. The pore pressure was 3MPa and oscillated in 20 seconds. The amplitude of oscillations ware 0.5 to 1.5 MPa. The hydraulic conductivity of fractured Kimachi sandstone was measured under different confining conditions (10,15,20,25MPa). The experimental results showed that of that the hydraulic conductivity of Kimachi sandstone increased due to the oscillation of the pore pressure when the confining pressure was over 10 MPa and the amplitude of the pore pressure was 1 MPa. It was also confirmed that this change in the hydraulic conductivity was sustained and does not return to the value before the oscillation. The experimental results obtained in this study indicate that the sustained increase of the groundwater level observed during the earthquake may change with the depth, which will lead to the understanding of the mechanism of groundwater level fluctuation due to the earthquake.