(Special session/Open call for public) YARO15: Research activities on rock engineering during the COVID-19 pandemic

[3K0101-08-06] [Student presentation:Doctoral course] Modification of the 2-D Simple Constitutive Model for Rocks based on the Strain-dependent Elastic Modulus

○Zhaoxin Li¹, Yoshiaki Fujii¹, Jun-ichi Kodama¹, Daisuke FukudaFukuda¹ (1. Hokkaido University)

Chairman:Atsushi SAINOKI (Kumamoto University)

Keywords:2-D constitutive model for rocks, Strain-dependent elastic modulus, Class II strain-softening, Stress-dependent elastic modulus, Convex failure envelope

A simple 2-D constitutive model for rocks based on the strain-dependent elastic modulus has been proposed (Fujii and Ishijima, 1998). The model can simulate Class I and Class II strain-softening behavior and have the following similarities with actual rocks: (1) The tensile strength is less than the compressive strength; (2) The compressive strength increases with confining pressure; (3) The critical compressive strain increases with confining pressure; and, (4) The critical extensile strain is not affected by the confining pressure. However, the failure envelope, which should be convex for actual rocks, by the model was linear. Therefore, the model was modified by introducing stress-dependent elastic modulus based on the increase of secant Poisson's ratio with confining pressure. It was confirmed that the failure envelope became convex. The effects of the constants on the failure envelope were shown, and the procedure to approximate the stress-strain curves and failure envelope of rocks was proposed. Stress-strain curves and failure envelope of Paleogene Kamisunagawa sandstone under triaxial compression were simulated by two sets of parameters, and the second parameter set gave better results for post-peak behaviors.