A three dimensional constitutive law for swelling rock is presented. It can be applied to the osmotic swelling of mudstone as well as to the swelling of rocks containing anhydrite. It describes the development of time-dependent strains and stresses due to swelling considering elastic and viskoplastic behaviour. Furthermore an anisotropic swelling behaviour can be considered. This constitutive model was implemented within a numerical computation program according to the finite element method and calibrated on the basis of the results of measurements in the investigation drift of the Freudenstein tunnel which is completely located in the unleached Gypsum Keuper. A parameter combination could be found which results in a good agreement between numerical solutions and results of measurements. Therewith an analysis procedure which enables the design of tunnels in swelling rock is available.
Im vorliegenden Beitrag wird ein dreidimensionales Quellgesetz vorgestellt, das nach derzeitigem Kenntnisstand sowohl auf das osmotische Quellen von Tonsteinen als auch auf das Quellen anhydrithaltiger Ton- beziehungsweise Schluffsteine anwendbar ist. Das Stoffgesetz wurde in ein Finite-Elemente-Programm implementiert und anhand von Meßergebnissen des im unausgelaugten Gipskeuper liegenden Untersuchungsstollens des Freudensteintunnels kalibriert. Es ist gelungen, eine Kennwertkombination zu finden, mit der alle Meßergebnisse gut beschrieben werden können. Damit steht ein Bemessungsverfahren fuer Tunnel in quellfahigem Gebirge zur Verfuegung.
Dans l'article present un loi de gonflement à trois dimensions est presente, qui peut être applique aussi bien au gonflement osmotique de l'argile compactee q'au gonflement de l'argile compactee ou du limon compacte contenant de l'anhydrite. Le loi de comportement etait implemente dans un programme numerique d'elements finis et calibre avec des resultats de mesures de la galerie de recherche du tunnel de Freudenstein, situe dans le Keuper de gypse non lessive. On est reussi à trouver une combinaison de paramètres avec laquelle tous les resultats de mesures peuvent être bien decrits. Par ce moyen, une methode de dimensionnement existe pour des tunnels dans de la roche capable de gonfler.
(Figure in full paper)
For the Stuttgart 21 project, tunnels have to be driven in unleached gypsum Keuper. This rock mass consists of a horizontal alternating sequence of sulphate-containing clay-and siltstone and pure sulphate rock. The sulphate is found in two different modifications, as gypsum and as anhydrite. Both modifications can be found in rock at the same time if the rock is dry. If water gains access to the rock, however, anhydrite (CaSO4) transforms into gypsum (CaSO4 - 2H2O) by taking up two water molecules. This chemical process results in an increase of the solid volume by about 61%. Correspondingly, just as by the adsorption of water by swelling clay minerals, major swelling deformations can be caused.
In the past, this has led to major floor heave in many railway and road tunnels (2,6). In case of the over a hundred year old railway tunnel through the Kappelesberg at the German Rail line Waiblingen - Schwabisch Hall-Hessental for example, swelling has caused a heave of several metres in the area of the unsupported floor over the decades. This heave has led to the considerable camber in the originally horizontal strata that is visible in Fig. 1.
