The Kaiser Effect under Multiaxial Nonproportional Compression of Sandstone

The regularities of deformation and fracture of sandstone under nonproportional biaxial and triaxial cyclic compression accompanied by the rotation of the Lamé ellipsoid and in situ continuous detection of acoustic emission are investigated experimentally on the “Triaxial Independent Loading Test System” at the Ishlinskii Institute for Problems in Mechanics, Russian Academy of Sciences. It is found that the manifestation of the Kaiser effect in the current cycle of multiaxial nonproportional compression depends on the behavior of the size, shape, and orientation of the Lamé ellipsoid with respect to the previous cycle. The Kaiser effect is observed in the case when the material has already been subjected to active loading corresponding to the set orientation of the stress ellipsoid. The degree of the specified-effect manifestation is determined by the behavior of the shape of the Lamé ellipsoid.