異方性体としての花崗岩の弾性率に関する実験的研究

抄録

Granitic rocks have an orthotropic (rhmbic) elasticity. In quarryman's terminology, these anisotropic planes are called a rift plane, a grain plane and a hardway plane in the order of ease of splitting. The axes R, G and H are normal to these planes. In the anisotropic body, three independent elastic wave velocities in all directions exist. These are the velocities of the quasi-longitudinal wave involving shear motion, and of two quasi-shear waves involving dilatational motion. These velocities can be determined by nine stiffness constants for orthtropic materials with Kelvin-Christoffel's equation. In this study, two octadecahedrons and three trioctagonal prisms whose axes coincide with H, G and R of Oshima granite were used to determine the velocities of various directions of propagation and polarization. The nine independent stiffness constants were determined by the nine independent velocities. The polyhedron was loaded up to 200MPa under hydrostatic pressure. All components of the stiffness constants increased with an increase of pressure, showing that the anisotropy of the granite should be attributed to the pre-existing microcracks.