AN ELASTOPLASTIC STRAIN-HARDENING AND STRAIN-SOFTENING CONSTITUTIVE MODEL FOR SOFT ROCK CONSIDERING THE INFLUENCE OF INTERMEDIATE STRESS

FENG ZHANG, ATSUSHI YASHIMA, GUANG LIN YE, TOSHIHISA ADACHI and FUSAO OKA

ABSTRACT: In this paper, by introducing a tij concept and Matsuoka-Nakai failure criteria into the model proposed by Oka and Adachi, a modified strain-softening model is developed to consider the influence of the intermediate principal stress that may greatly affect the strength and stress-dilatancy relation of geologic materials under different loading paths. The original characteristics of the model, such as the ability to describe not only the strain softening behavior of soft rock but also the stress-dilatancy relation, the ability to obtain a unique solution for initial value and boundary value problems in a finite element analysis, remain valid in the modified model. Its validity is verified by compression tests on artificial soft rock under plane-strain condition.

Key words: constitutive model, intermediate stress, soft rock, strain softening (IGC: F6)