Creep Behavior of Mélange Rocks and the Hardening-Damage Nonlinear Elastic-Viscous Model

This study aims to establish a mode for representing the creep behavior of mélange rock in various underground geoengineering projects. We conducted multi-stage triaxial compression creep tests to investigate key aspects of creep behavior, including the evolution of the creep rate, cumulative creep strain, and long-term strength. The results indicate that the creep rate curves exhibit a trend resembling a parabolic function, approaching their minimum values as they converge to long-term strengths. The cumulative creep strain to total strain ratio ranges from 0.245 to 0.2917 across different confining pressures (5, 10, 15, and 20 MPa). Additionally, long-term strengths extracted from isochronous curves of dimensionless variables are consistently aligned with the maximum creep strain to elastic strain ratio, falling within a stress ratio range of 0.75 to 0.82. To model this behavior, we propose a Hardening-Damage Nonlinear Elastic-Viscous framework comprising two nonlinear viscous elements and an elastic element configured in a serial link structure, following the principles of Maxwell’s model. The parameters and coefficients of this model were evaluated against the multi-stage creep test results, confirming its effectiveness in replicating the creep behavior of mélange rock. The proposed model, characterized by a limited number of coefficients related to material properties, simplifies the analysis. Ultimately, this work aids in evaluating the stability of deep-underground tunnel surrounding mélange rock masses.