Abstract
A rock creep constitutive model is the core content of rock rheological mechanics theory and is of great significance for studying the long-term stability of engineering. Most of the creep models constructed in previous studies have complex types and many parameters. Based on fractional calculus theory, this paper explores the creep curve characteristics of the creep elements with the fractional order change, constructs a nonlinear viscoelastic-plastic creep model of rock based on fractional calculus, and deduces the creep constitutive equation. By using a user-defined function fitting tool of the Origin software and the Levenberg–Marquardt optimization algorithm, the creep test data are fitted and compared. The fitting curve is in good agreement with the experimental data, which shows the rationality and applicability of the proposed nonlinear viscoelastic-plastic creep model. Through sensitivity analysis of the fractional order β2 and viscoelastic coefficient ξ2, the influence of these creep parameters on rock creep is clarified. The research results show that the nonlinear viscoelastic-plastic creep model of rock based on fractional calculus constructed in this paper can well describe the creep characteristics of rock, and this model has certain theoretical significance and engineering application value for long-term engineering stability research.
Highlights
IntroductionRock rheology is a process in which the rock mineral structure is constantly adjusted with time, resulting in the continuous change of stress and strain state with time [1,2,3,4,5,6,7]
Rock rheology is a process in which the rock mineral structure is constantly adjusted with time, resulting in the continuous change of stress and strain state with time [1,2,3,4,5,6,7].e rheological effect of rock is obvious in slope, tunnel, roadway, and other projects, which is a very important feature of rock materials [8,9,10,11,12,13]
Rock creep is an important part of rock rheological mechanics theory, and research on rock creep constitutive models is the core content of the theory [18,19,20,21]. erefore, research on rock creep constitutive models will have very important theoretical significance and practical engineering value
Summary
Rock rheology is a process in which the rock mineral structure is constantly adjusted with time, resulting in the continuous change of stress and strain state with time [1,2,3,4,5,6,7]. By discussing the influence of the change in fractional order on the creep characteristic curve of rock, creep elements of different orders are innovatively used to construct a nonlinear viscoelastic-plastic creep model of rock, and a nonlinear creep model of rock with fewer parameters is developed using fewer elements. On this basis, the creep test results are nonlinearly fitted to verify the rationality and applicability of the constructed model
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