ABSTRACT

: To understand characteristics of crack deformation in rock specimen, uniaxial compressive tests(UCT) with damage stresses were performed with granites. Elastic wave velocity was measured on natural saturation condition after UCT with different stress levels and after saturation test. Changes of elastic wave velocities imply that there has been development or displacement of cracks induced by the UCT and the deformation has made some space to contain fluid. The water contents of the specimens which were experienced UCT show higher values than those which were measured before UCT. These changes can be explained by the fact that deformation of cracks induced by UCT increases space to contain more water. Results of permeability tests for the deformed specimens are applicable to low permeable and impermeable class. Relationship of crack length and difference of crack density with permeability coefficient indicates that connectivity of cracks plays an important role to control conductivity along cracks.

1 INTRODUCTION

Rock masses contain mechanical discontinuities such as micro crack, bedding, joint and fault in micro- or macroscopic scale. Excavation of rock masses induces initiation and propagation of discontinuities. The discontinuities play a role of conduit of groundwater flow and affect stability of rock masses and structures. In case of disposal site for high-level radioactive wastes, micro cracks might act as conduits of diffusion or migration of radionuclide which can be infiltrated from a canister. For the development of underground opening, therefore, it is an important thing to characterize changes of discontinuities and rock damages to determine stability of rock mass and structure.

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