A rational design of the support and lining structures can be achived only if the load sharing capacity of the rock mass is taken as far as possible into consideration. The proposed finite element model reproduces the structure-rock interaction phenomena. The rock mass can be nonhomogeneous and anisotropic and is considered to show viscous behaviour. The lining prestressing performed by grouting the surrounding rock with cement grout under high pressure is considered. In the first part of the paper the performances of the mathematical model are analysed in terms of the numerical results and the field measurements for two Romanian water power tunnels. In the second part of the paper, detailed discussions of the lining prestressing parameters are given.
Eine rationelle Aufstellung von Aussteifungs- und Vermantelungsarbeiten der hydrotechnischen Stollen kann man nur dann durchfuehren, wenn man die Übernahmefahigkeit des Felsengesteines von auβeren Beanspruchungen in Betracht zieht. Das vorgeschlagene mathematische Modell gibt Wechselwirkungserscheinungen zwischen der Struktur und dem Gesteinsmassiv wieder. Das Felsengestein kann ungleichartig und anisotrop sein, und man nimmt an, daβ es ein dichtfluessig-elastisches Verhalten aufweist. Die Vorspannung der Verkleidung wird durch Einspritzen des umgebenden Felsengesteines mit Zementmilch unter Druck durchgefuehrt. Im ersten Teil der Arbeit werden die Leistungen des vorgeschlagenen mathematischen Modells aufgrund des Vergleiches von Berechnungs- und Messungsergebnissen analysiert, die fuer zwei hydrotechnische, in Rumanien ausgefuehrte Stollen durchgefuehrt werden. 1m zweiten Teil der Arbeit werden die Parameter, von denen die Vorspannung der Verkleidung abhangt, ausfuehrlich behandelt.
Une etude raisonnable des travaux d''etoyage et de revêtement des galeries hydrotechniques n''est possible que si l''on envisage la capacite des roches de resister aux efforts exterieurs. Le modèle mathematique propose reproduit lesphenomènes d''interaction entre la structure et Ie massif rocheux. La roche peut être non homogène et anisotrope et on lui attribue un comportement visco-elastique. La precontrainte du revêtement est realisee par l''injection de la roche avoisinante de lait de ciment sous pression. Dans la première partie de l''ouvrage on analyse les performances du modèle mathematique propose sur la base de la comparaison entre les resultats des calculs et ceux des mesures effectues pour deux galeries hydrotechniques mises en oeuvre en Roumanie. Dans la seconde partie de l''ouvrage on presente en detail les paramètres dont depend la precontrainte du revêtement.
For water power plant tunnels a rational design of the support and lining structures can be achived only if the load sharing capacity of the rock mass is taken as far as possible into consideration.
An elastic support structure. according with NATM principle, has the purpose of transforming the rock surrounding the tunnel profile from a load-exerting into a load-carrying member of the system. The lining structures of the pressure tunnels with large internal pressures are designed function of the amount of the preesure load which can be transfered to the rock mass. Basically. both unreinforced and reinforced concrete linings are quite unsuitable for one of the most important tasks, namely the prevention of water losses because of their low tensile strength. Consequently, a so-called passive prestressing is promoted, where the prestressing is produced by surrounding rock, as support or active element. In the last decades. for many pressure tunnels the prestress has been applied by grouting the surrounding rock mass and forcing the cement grout under high pressure into the rock cracks and discontinuities. The final lining stresses are dependent of the prestressing reduction due to the concrete creep, of the viscous flow of the rock mass and of the pressure rising schedule. The proposed mathematical model. based on the finite element concept, takes into account all these structure - rock interaction phenomena. The behaviour of tunnel support and lining structures is analysed for plane strain conditions. The three-dimensional effects of the tunnel face advancing are taken into considerations by introducing the "equivalent initial stress" artifice. The rock mass can be nonhomogeneous and anisotropic, and is considered to show viscous behaviour associated with the deviatoric deformations during the excavation process, and with the radial deformations under the internal pressure loading. The rock bolting effects are reproduced by changing the elastic properties of the surrounding rock and introducing a radial anisotropy. The shotcrete placement effects are reproduced by introducing a ring of finite elements with in time increasing Young modulus, according to shotcrete grow in strength. The tunnel lining prestressing process is reproduced by considering the grout pressures as a hydrostatic state of residual stresses and then evaluating the lining stressing due to the residual stress relief. The time-dependent behaviour of both rock and lining is considered by the plastic flow of the concrete lining and by the rock stress relaxation.
