Error-controlled implicit time integration of elasto-visco-plastic constitutive models for rock salt |
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| Authors: | Ning Zhang Thomas Nagel |
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| Institution: | 1. School of Science, Nanjing Univerity of Science and Technology, Nanjing, China;2. Geotechnical Institute, Technische Universität Bergakademie Freiberg, Freiberg, Germany |
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| Abstract: | The mechanical behavior of rock salt is rate-dependent at different time scales. Using caverns in rock salt formations for renewable energy storage implies that the underground structures are subjected to both short-term and long-term loads, increasing robustness and flexibility requirements for numerical simulators used to assess the safety of such structures. So far, explicit time integration with model-specific heuristics for time-step size determination dominate in application studies. In this paper, the suitability of error-controlled adaptive time-integration schemes of the diagonally implicit Runge-Kutta type is investigated in comparison with the Backward Euler and Crank-Nicolson schemes when applied to the integration of typical elasto-visco-plastic constitutive models of rock salt. The comparison is made both for monotonic and for cyclic loads as well as taking account of thermo-mechanical coupling. Analyses of the time-integration errors and the time step-size evolution show the suitability of the integration scheme for these material models. The automatic adjustment of the time-step size was found to be robust across all material models and boundary conditions as well as for non-isothermal situations for a single algorithmic parameter set. |
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| Keywords: | error control implicit Runge-Kutta rock salt time adaptivity viscoplasticity |
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