Anisotropic Behavior of Soft Sedimentary Rock and A Constitutive Model

Abstract

In order to investigate the anisotropic behavior of soft sedimentary rock, a series of triaxial compression tests are performed on Tomuro stone, sampled in different directions. From the test results, it is confirmed that the deformation characteristics and strength are strongly dependent on the direction; in other words, Tomuro stone is a transversely isotropic body. The authors have developed an anisotropic elasto-plastic constitutive model which can describe anisotropic behavior through triaxial tests. The model is based on the elasto-plastic constitutive model with strain softening proposed by Adachi and Oka (1995). In the formulation of the model, a generalized Hooke's law is adopted for the elastic strain increment, and the transformation stress concept proposed by Boehler and Sawczuk (1977) is used for the plastic strain. Five independent elastic moduli are used for the transversely isotropic body, and three independent parameters are introduced for the plastic anisotropy. These parameters can be determined from the triaxial compression tests performed with specimens sampled in different directions. Comparisons between the experimental data from triaxial tests and simulated results from tests using the model indicate that the proposed constitutive model can well reproduce the direction dependent behavior of soft sedimentary rock.