For a large underground power station located in Portugal, an extensive rock mechanics test program was performed. The aims of the in situ tests are ~he quantification of the state of stress using the stress tensor tube and the small flat jack methods, and the deformability of the rock mass using the large flat jack method. Laboratory tests were also carried out, namely joint shear tests and uniaxial compressive tests, and field investigations were performed for the characterization of sets of rock mass discontinuities.

The interpretation of in situ stress measurements was made by a suitable methodology that involves the use of a large tridimensional boundary element model.


On a realise un vaste programme d´essais de mecanique des roches pour une· importante centrale souterraine situee au Portugal. Les essais sur place ont vise la quantification de l´etat de contrainte au moyen de la methode STT et de la methode des petits verins plats; la deformabilite du massif rocheux a ete investiguee par la methode des grands verins plats. On a aussi mene des essais au laboratoire, particulierement des essais de cisaillement de diaclases et des essais de compression uniaxiale, et des etudes sur place pour caracteriser les familles de discontinuites du massif rocheux.

L'interpretation des mesures de contraintes in situ a ete faite selon une methodologie appropriee ayant en recours à l´utilisation d´un modèle tridimensionnel d´elements de frontière.


Fur ein großes, unterirdisches, in Portugal gelegenes Kraftwerk wurde ein umfangreiches Felsmechanikversuchsprogramm durchgefuehrt. Der Zweck der in-situ Versuche ist die Quantifizierung des Spannungszustandes, mittels der Stress-Tensor-Tube und der Small-FIat-Jack Methoden, und der Felsverformbarkeit, mittels der Large-FIat-Jack Methode. Es wurden auch Laborversuche ausgefuehrt, namentlich, Kluftscherversuche und einaxiale Druckversuche, und Felduntersuchungen fuer die Kennzeichnung der Felstrennflachen scharen durchgefuehrt.

Die Interpretation der In-situ-Spannungsmessungen geschah mittels einer angebrachten Methodologie, die den Gebrauch eines großen, dredimensionalen Grenzwert-Element-Modells einschließt.


The 2x300 MW Alto Lindoso hydro-electric scheme on the Lima river, in the northern Portugal includes mainly an arch dam 110 m high, a hydraulic circuit consisting of two parallel short headrace tunnels followed by pressure shafts of about 250 m, connecting to the underground powerhouse; after the powerhouse two draft tubes join in 389 the surge chamber, 21 m in diameter and about 70 m high, and a tailrace tunnel follows, 8.3 m in diameter and about 5 km long (Fig. 1), (Sousa Neves 1986).,





Fig. 1 Alto Lindoso scheme In the design stage a detailed geologic and geomechanical study was conducted, based on surface observation, mechanical exploration, geophysical surveys, stress measurements in boreholes, deformability measurements with conventional systems and with LNEC's dilatometer, shear tests and several laboratory tests (LNEC 1965, 1977), (Cotelo Neiva et al. 1983). Though boreholes had not reached depths exceeding about 100 m, they made it possible to take decisions as to the options initially put forward in the design Btage.

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