Effect of Water on Stability or Instability of the Shear Fracture Process of Rock.

Abstract

In order to clarify the effect of water on stability or instability of the shear fracture process of rock, it is critical to study the influence of water on the constitutive properties of the shear fracture process. For this purpose, experiments on fracture of intact granite rock samples have been performed under dry and wet conditions at the following two temperatures: 270 degrees C and 450 degrees C. The experimental results indicate that the shear fracture stability or instability is not affected by the magnitude of pore water pressure, but it is strongly affected by temperature; the shear fracture process is stabilized at temperatures higher than 300 degrees C. The peak shear strength increases linearly with the effective normal stress at temperatures below 300 degrees C. At temperatures above 300 degrees C, however, the peak strength is lower than that expected from the effect of the effective normal stress. It is discussed how water released by a decomposition reaction of hydrous minerals contained in rock affects stability or instability of the shear fracture.