Contributions to the simulation of salt concrete - Short- and long-term mechanical behavior description involving an advanced plasticity model approach
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In the former German concept, rock salt was the favorite host rock to dispose heat-generating radioactive waste. To assure the integrity of the complete repository system after closure, shafts and drifts have to be sealed. In the context of the DOPAS project GRS performed a laboratory test program and numerical simulations to investigate the properties of concrete based sealing materials. The test program and the numerical simulations mainly focused on salt concrete. In order to perform the numerical simulations, the finite-element-method program Code_Bright was employed. Former attempts of simulating the short-and long-term mechanical behavior of salt concrete yielded insufficient results with respect to the reproduction of 1) volumetric strains, 2) a stress reduction as a respond to the damage within the sample and 3) viscoplastic strains upon passing a deviatoric stress level above 20 MPa. Among other modeling approaches, an advanced plasticity constitutive model has been taken into account, which is currently being developed. It enables the simulation of 1) strain-hardening prior peak, 2) peak strength, 3) strain-softening post peak and 4) time-dependent creep deformations. A detailed assessment has already revealed the applicability of the new constitutive model in terms of describing the creep behavior. The present thesis pursues the objective of reproducing the entire mechanical behavior of salt concrete by means of employing the advanced plasticity constitutive model. Moreoverit is envisaged to identify limitations of the model and to mention further development needs finally.