Abstract
Dense sands, overconsolidated clays and soft rocks show strain-hardening and strain-softeing behavior in a certain range of confining pressure. The aim of the present paper is to construct a constitutive model of soft rocks that can describe not only strain-hardening but also strain-softening behavior. The constitutive model is derived by introducing a stress history tensor. The derived constitutive model is examined by comparison of the calculated results with experimental results of sedimentary soft rock (porous tuff). In addition, the applicability of the model to numerical analyses is discussed in relation to the uniqueness of the solution in an initial and boundary value problem.
