木元 小百合

In order to investigate anisotropic behavior of soft sedimentary rocks, a series of triaxial compression tests are performed for Tomuro stone. Prom the test results, it is confirmed that Tomuro stone is transversely isotropic body. The authors have developed an anisotropic elasto-plastic constitutive model which can describe the anisotropic behavior obtained from triaxial tests. The model is based on Adachi and Oka (1995) ’s elasto-plastic constitutive model with strain softening. In the model, the generalized Hooke’s law is adopted for elastic strain increment, and transformation stress concept is used for plastic strain. Comparisons between experimental data and simulated results, indicate that the proposed constitutive model can well reproduce the direction dependent behavior of soft sedimentary rocks.

The aim of the present paper is to study strain localization problem of water-saturated clay using an elasto-viscoplastic model that is applicable to both normally and orverconsolidated clays. First, instability of the model under undrained creep conditions was analyzed in the sense of acceleration creep failure. Instability analysis shows that overconsolidated clay with positive dilatancy is more unstable compared with the normally consolidated clay with negative dilatancy. Then, finite element analysis of deformation of water saturated clay is presented under plane strain conditions. Numerical results is consistent with the non-linear instability analysis.

In the present paper, effect of dilatancy on strain localization was numerically studied for dilatant and contractant clays using a newly developed elasto-viscoplastic constitutive model which can be applied to both normally and overconsolidated clays. From the present numerical analysis, it was found that dilatancy characteristics plays an important role in the strain localization behavior.