20 th International Conference on the Application of Computer Science and Mathematics in Architecture and Civil Engineering K. G ¨ urlebeck and T. Lahmer (eds.) Weimar, Germany, 20-22 July 2015 PARAMETER IDENTIFICATION APPLYINGIN COMPLEX THERMO-HYDRO-MECHANICAL PROBLEMS LIKE THE DESIGN OF BUFFER ELEMENTS L. Nguyen-Tuan ∗ , T. Lahmer, M. Datcheva, E. Stoimenova and T. Schanz ∗ Institute of Structural Mechanics and Juniorprofessorship Optimisation and Stochastics, Bauhaus-Universit¨ at Weimar Marienstrasse 15, 99423 Weimar, Germany E-mail: long.nguyen.tuan@uni-weimar.de Keywords: Parameter Identification, Coupled THM Problem, Sensitivity Analysis, Particle Swarm Optimisation, Confidence Interval. Abstract. This study contributes to the identification of coupled THM constitutive model pa- rameters via back analysis against information-rich experiments. A sampling based back anal- ysis approach is proposed comprising both the model parameter identification and the assess- ment of the reliability of identified model parameters. The results obtained in the context of buffer elements indicate that sensitive parameter estimates generally obey the normal distri- bution. According to the sensitivity of the parameters and the probability distribution of the samples we can provide confidence intervals for the estimated parameters and thus allow a qualitative estimation on the identified parameters which are in future work used as inputs for prognosis computations of buffer elements. These elements play e.g. an important role in the design of nuclear waste repositories. 160