A three-dimensional elastic constitutive model for rock salt is proposed. This stress strain law takes into account the three phases of creep (transient, steady state and accelerated creep), dilatancy, as well as the failure and post failure behaviour. The model was implemented into a finite element program and validated on the results of laboratory tests and in situ measurements. A good qualitative and quantitative agreement with the test and measurement results is achieved. A stability analysis for an underground repository in rock salt is presented.


Es wird ein dreidimensionales elastisch-viskoplastisches Stoffgesetz fuer Steinsalz vorgestellt. Mit diesem Stoffgesetz können die drei Kriechphasen (primares, sekundares und tertiares Kriechen), Dilatanz sowie das Bruch- und Nachbruchverhalten erfaßt werden. Dieses Modell wurde in ein Rechenprogramm, das auf der Methode der finiten Elemente basiert, implementiert und an Ergebnissen von Laborversuchen und in-situ-Messungen validiert. Die Versuchs- und Meßergebnisse lassen sich mit diesem Stoffgesetz qualitativ und quantitativ gut nachvollziehen. Als Anwendungsbeispiel wird der Standsicherheitsnachweis fuer eine Untertagedeponie im Steinsalz erlautert.


Cet article presente un modele constitutive elastique/viscoplastique à trois dimensions pour sel gemme. Ce modele comprend les trois stade de fluage (fluage primaire, secondaire et tertiaire), la dilatation, le comportement de defaillance et d'apresdefaillance. Il est implante dans un programme de calcul aux elements finis. À l'aide des essais laboratoire et des mesures in situ, le modele a ete valide. Les resultats des essais et des mesures concordent qualitatifs et quantitatifs aux resultats des calculations.


World wide, salt deposits are not anymore used only for mineral exploitation, but to an increasing extent also for the underground storage of gases and fluids and as underground repositories for hazardous or radioactive waste. Because of this, the importance of questions regarding the excavation and stability of openings in salt rock increases continuously. The design and the stability analysis for openings in salt rock necessitates a model for the realistic description of the stress-strain behaviour of rock salt. In the following, a constitute law is presented, which has been developed by Kiehl, Erichsen and Döring (1998) and is an extension and advancement of the constitutive laws of Wallner (1983) and Döring and Kiehl (1996).

Fig. 1 schematically illustrates the form of creep curves as obtained with uniaxial creep tests, which are unconfined compression tests with a constant load (σ = const.). The stress σ leads to elastic deformations εel not depending on time as well as to creep deformations εc depending on time. If the creep stress σ is smaller than a stress σF, the so-called uniaxial yield stress, the increase of the creep deformation with time, i. e. the creep rate εc is largest after applying the creep stress and then converges to a constant value. The creep deformation can, in this case, be subdivided into two components. One is the so-called primary component of the creep deformation εp, which converges to a constant value and does practically not anymore increase after a certain time. Therefore, the primary creep is also called transient (nonsteady) creep.

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