Modeling in-situ desiccation cracks in a ventilated niche using homogeneously and randomly distributed material parameters

Assessing barrier integrity under varying environmental conditions is crucial in the context of radioactive waste disposal. This study, originally  conducted at the Mont Terri Rock Laboratory in Switzerland within the Cyclic Deformation (CD-A) experiment, gains new understanding in this context. The laboratory, located within an Opalinus Clay formation, has been also instrumented to observe the triggers of desiccation cracking in open and closed excavations. Seasonal changes play an important role especially during winter where the relative air humidity reduces and drives desiccation cracking. To model this dynamic, we employed a hydro-mechanical model incorporating macroscopic poromechanics, the Richards equation for partial saturation and the phase-field modeling approach for cracking. Key to our study was the evaluation of unsaturated hydro-mechanical responses using field-acquired parameters such as the measured crack apertures, supplemented by existing literature. We established a good correlation between the observed and calculated crack formation by using the measured seasonal changes in relative air humidity as boundary condition as well as using  homogeneously and randomly distributed material parameters [1]. Furthermore, our study delves into the implications of enhanced permeability due to cracking on barrier integrity. Our findings offer insights into the dynamics of crack development and their implications, thereby making an  incremental contribution to the broader goal of ensuring safe and effective management of radioactive waste disposal.

[1] T. Cajuhi, G. Ziefle, J. Maßmann, T. Nagel and K. Yoshioka, Modeling desiccation cracks in Opalinus Clay at field scale with the phase-field approach. InterPore Journal (in press).