ABSTRACT:

The Castelo do Bode tunnel is part of the water system to the Lisbon area and is located immediately after the Castelo do Bode reservoir. Particular importance was given to the verification of the safety and serviceability of this important underground structure. Loading tests were performed with slow and fast filling up of the tunnel. Observed results obtained during the tests for an instrumented section were compared with values obtained by means of numerical and analytical solutions for impervious and pervious linings. It has been possible to state as a general conclusion, that the tunnel has the adequate safety and service ability conditions.

RÉSUMÉ:

La galerie du Castelo do Bode est une part du système de fourniture d'eau à la region de Lisbonne et il est situe irnmediatement après la retenue du Castelo do Bode. Une particulière importance a ete donnee à la verification de la securite et des conditions de fonctionnement de cette importante structure souterraine. Des essais de charge ont ete effectues avec le remplissage lent et rapide de la galerie. Les resultats observes obtenus lors des essais pour une section instrumentee ont ete compares avec les valeurs obtenues à travers solutions numeriques et analytiques pour des revêternents irnpermeables et permeables. Il a ete possible de considerer cornrne conclusion generale, que la galerie possède les conditions de securite et de fonctionnement adequates.

ZUSAMMENFASSUNG:

Der Castelo-do-Bode-Tunnel ist Teil des Wassersystems der Lissaboner Gegend und schlieβt sich unmittelbar an das Castelo-do-Bode-Reservoir an. Eine besondere Aufmerksamkeit wurde der Überpruefung von Sicherheit und Tauglichkeit dieser wichtigen Untergrundstruktur gewidmet. Es wurden Belastungsversuche mit langsamem und schnellen Fuellen des Tunnels durchgefuehrt. Die wahrend der Versuche an einem Querschnitt erhaltenen Ergebnisse wurden mit den Wert en verglichen, die numerische und analytische Lösungen fuer durchlassige und undurchlassige Auskleidungen ergeben hatten. Es konnte die allgemeine Schluβfolgerung gezogen werden, daβ der Tunnel die entsprechende Sicherheit und Tauglichkeit besitzt.

1 INTRODUCTION

The new water supply system to the Lisbon area starts at the Castelo do Bode reservoir, and includes a l25km long conduit. The Castelo do Bode tunnel is part of this system and is located immediately after the reservoir. It has a 3m diameter circular section, a length of 1088m, and allows a maximum flow of 106m3/day(EPAL, 1988). The support is a reinforced concrete lining with the exception of the last 150m, where a steel lining exists. Figure 1 shows the location of the tunnel. LNEC gave a considerable contribution to the geotechnical characterization of the rock mass crossed by the tunnel and to the determination of the in situ state of stress, as well as to the implementation and execution of the observation system. Having this in mind, loading tests were performed with slow and fast infilling of the tunnel. Observed results obtained during the tests for an instrumented section were compared with values obtained by means of numerical and analytical solutions for impervious and pervious linings.

2 ROCK MASS CHARACTERIZATION

The tunnel was excavated in a very tectonized pre- Cambrian metamorphic complex consisting of gneisses and migmatites very similar to those which form the Castelo do Bode dam foundation. Some pegmatite, aplite and quartz veins with a maximum thickness of 10cm cross the entire rock mass. The rock mass outcrops are generally highly weathered (class W4 of the ISRM classification) and some thin colluvial deposits occur at several locations (Oliveira et al., 1983). The gneissic formations were subjected to high tectonic stresses throughout their geological history. Nevertheless, the attitude of the gneissose fabric is very much the same along the alignment of the tunnel.

This content is only available via PDF.
You can access this article if you purchase or spend a download.