Postfailure lateral deformation of rock specimen under the triaxial compression test

To estimate the stability of rock caverns is one of the most important problem on mining and civil engineering. The stability is not estimated correctly on the stage of design, because the deformation behavior of rock in the loosed region is not sufficiently clear. Therefore, investigation of the postfailure lateral deformation of rock is necessary by conducting triaxial compression tests. In this study, we used the measuring system composed of eight displacement transducers of cantilever type and a data logger with very fast channel scanner and large capacity of data storage for measuring the lateral deformation of rock specimen under the triaxial compression test. Consequently, we could measure the lateral deformation in every 45 degree of radial direction even under the postfailure condition. Moreover, the behavior of the lateral deformation could be understood quantitatively by the analysis with classifying the deformation into the four modes of deformation, (a) isotropic deformation, (b) anisotropic deformation caused by the anisotropy of rock specimen, (c) horizontal movement of the specimen caused by the testing conditions and (d) anisotropic deformation caused by the shear displacement along the fracture surface. In addition, the point where the apparent fracture was generated could be detected by the starting point of mode (d) even though the apparent stress drop was not seen on the stress-strain curve.