After calling the attention to the importance of the hydromechanical interaction in pressure tunnels and shafts, the paper describes briefly a finite element numerical model of the hydromechanical behaviour of fractured rock masses. The mechanical and hydraulic behaviours are modelled separately, and the hydromechanical coupling is obtained using an iterative procedure. Both the mechanical and the hydraulic models are suitable for quasi-plane analyses of multilaminated media and can include discrete joints. In order to enhance the importance of hydromechanical coupled analyses for a correct understanding of the behaviour of pressure tunnels and shafts two parametric studies of a pervious thick walled cylinder and of a concrete lined pressure tunnel with an initial gap between the lining and the rock mass are then presented.


Après avoir montre l'importance de I'interaction hydromecanique en tunnels et puits sous pression, on fait une bref description d'un modèle numerique en elements finis du comportement hydromecanique des massifs rocheux fractures. Les comportements mecanique et hydrauliques sont modelises separement et le couplage hydromecanique est obtenu par une procedure iterative. Les modèles mecanique et hydraulique sont tous les deux souhaitables pour des analyses quasi-planes des milieux multilamines et peuvent inclure des joints isoles. Sont finalement presentes deux etudes parametriques qui montrent l'importance des analyses hydromecaniques couples, pour une bonne comprehension du comportement des tunnels et des puits sous pression.


Nachdem auf die wichtigkeit der hydromechanischen Interaktion aufmerksam gemacht wurde, beschreibt diese Arbeit kurz ein numerisches Modell finiter Elemente des hydromechanischen Verhaltens von geklueftetem Fels. Das mechanische und das hydraulische Verhalten werden in getrennten Modellen dargestellt; die hydromechanische Kopplung wird durch ein Iterativverfahren erhalten. Sowohl das mechanische als auch das hydraulische Modell sind fur "quasi-plane" Analysen von vielschichtigen Medien geeignet, und können isolierte Kluefte mit einschlieβen. Um die Bedeutung von hydromechanischen Analysen fuer ein korrektes verstandnis des Verhaltens von Druckstollen und Druckschachten hervorzuheben, werden zwei Parameter-Studien, eines dickwandigen durchlassigen Rohres und eines mit Beton ausgekleideten Druckstollen mit einer urspruenglichen Spalte zwischen Beton und Fels, vorgestellt.


Unlined and concrete lined pressure tunnels and shafts are typical kinds of underground openings where the interaction between mechanical and hydraulic problems must be considered for an adequate design and safety evaluation. The existence of this interaction makes it important to study them as an integrated process, i.e., in a coupled way. The hydromechanical behaviour of fractured rock masses is influenced in a decisive way by the presence of joints. They are responsible in a large extent for the seepage which occurs through the rock mass, and are also the most sensitive elements of the rock mass with respect to deformation under stress changes. As water flow through a joint is highly dependent on its characteristics, namely aperture, which is very influenced by the state of stress, hydromechanical studies of fractured rock masses must pay special attention to the role of joints and to a correct assessment of their properties. In the particular case of pressure tunnels and shafts, the importance of the hydromechanical interaction is influenced by the type of lining that is used. In the case of steel linings, this problem is not relevant, since the flow of water from or into the rock mass does not take place. However, this is an expensive solution and nowadays, owing to the progresses made in understanding the behaviour of the composite structure formed by the rock mass and the lining, in the techniques of rock mass improvement and in the use of pre-stress in concrete linings, the use of steel lining is usually restricted to zones where the rock mass properties.

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