Abstract
Through a series of drained triaxial compression tests covering wide-rang confining pressures, the effect of the confining pressure on the deformation and failure of the soft rock are studied. The test sample used is a porous quality tuff called Tomuro-ishi. The material parameters used in the strain softening type elasto-plastic constitutive equation proposed by Adachi and Oka (1992) are obtained from the present test results, and most of them show the confining pressure dependency. Therefore, these parameters are formulated as a function of the confining pressure and the confining pressure dependencies are incorporated in the original Adachi & Oka model. As a result of test simulations, it is shown that the proposed model can well explain the experimental results under different confining pressures in the common basic soil parameters.
