A finite element implementation of strain-softening rock mass

Many types of rock masses behave in a strain-softening way in geotechnical engineering. Numerical methods have to be used to study these kinds of media. But a limit to the rate of softening of the strain-softening material exists within the framework of the classical theory of plasticity. Considering the salient characteristic that the strength parameters decrease during the process of strain-softening, this paper develops a procedure for modeling strain-softening behavior based on the methodology for analyzing brittle-plastic rock mass. In the proposed procedure, strain-softening process is simplified as a series of stress drops and plastic flow. Therefore, solving a strain-softening problem becomes finding a series of brittle-plastic solutions. The proposed procedure is implemented in a finite element code based on the classical theory of plasticity in which Mohr–Coulomb (M–C) criterion is employed. Numerical examples are examined and the results validate the proposed implementation.