Temperature-confining pressure coupling effects on the permeability of three rock types under triaxial compression

Triaxial compression tests were carried out at 295K and 353K under confining pressure of 1-15 MPa for Shikotsu welded tuff, Kimachi sandstone and Inada granite. The samples were kept for 24 hr consolidation and then axial compression was applied measuring permeability. Permeability decreased monotonously for Shikotsu welded tuff. The permeability decreased first, began to increase before peak load and showed almost constant value in the residual strength state for Kimachi sandstone and Inada granite. Permeability decreased by failure for Shikotsu welded tuff. It increased due to failure under low confining pressures but decreased under high confining pressures for Kimachi sandstone. It increased due to failure for Inada granite. The permeability at 353K was lower than that at 295K for all of the three types of rock. The mechanisms of the permeability decrease are also shown.