ABSTRACT:

Squeezing conditions were encountered in the tailrace tunnel during construction of the Uri Hydroelectric Power Plant, in Kashmir, India. The final tunnel was to be finished with a stiff concrete lining. To permit casting, even though deformations were still in progress, the pressures that would develop had to be properly anticipated. In order to do this, the work was carried out in three stages. The deformations were first observed, then a conceptual model of the squeezing behaviour was established and finally the model was tested with a full-scale test lining. The theoretical model turned out to underestimate the pressure, but stability was achieved as predicted.

RESUME:

Des pressions se sont manifestees dans la galerie de fuite pendant la construction du Projet Uri Hydroelectric en Cachemire aux Indes. La galerie definitive devait être terminee par un revêtement rigide de beton. Pour permettre Ie moulage du revêtement, même pendant les deformations, les pressions potentielles ont du être correctement anticipees. Dans ce but, Ie travail a ete realise en trois phases. On a d'abord observe les deformations, puis un modèle conceptuel du comportement des pressions a ete etabli et, enfin, Ie modèle a ete teste avec un revêtement à echelle reelle, Le modèle theorique s'est revele avoir sous-estime la pression, mais la stabilite a ete realisee com me prevue.

ZUSAMMENFASSUNG:

Wahrend des Baus des Auslauftunnels des Wasserkraftwerkes Uri in Kashmir, Indien wurde drueckendes Gebirge angetroffen. Der gesamte Tunnel wurde mit Beton ausgekleidet. Es mußte trotz Verformungen laufend betoniert werden, daher mußten die zu erwartender Veromungen richtig prognostiziert werden. Die Arbeit wurde deswegen in drei Schritten durchgfuehrt. Nachdem Verformungen festgestellt wurde, wurden zuerst ein Verformungsmodell erarbeitet, und schließlich wurde ein Versuchs Modelle Maßstab 1:1 vor Ort ausgefuehrt. Es stellte sich heraus, daß im Verformungsmodelle die Verformungsdruecke unterschatzt worden waren. Bei der entgueltigen Ausfuehrung der Tunnelinnenschale wurden aber die Erkentnisse aus den Versuchen und Modellen beruecksichtigt, und die Standsicherheit des definitiven Bauwerkes ist gewahrleistet.

1 INTRODUCTION

The Uri Hydroelectric Power Project is situated in the State of Jammu and Kashmir in north-western India. The power plant is supplied with water from the Jhelum River which has its springs in Kashmir and flows through the Kashmir Valley into Pakistan, where it becomes a tributary of the Indus River. The project is designed as a run-of-the-river scheme. The water is diverted from the river and lead from the head regulator and desilting basins into an 11-km long head race tunnel and two 210-m high pressure shafts. After passing through the four turbines in the machinery hall the water is lead through the draft tubes and the 2-km long tailrace tunnel back into the river. The headrace and tailrace tunnels are of horseshoe shape with a diameter of 9 m. The project is owned by the National Hydroelectric Power Corporation Ltd (NHPC). The construction of this hydro power project is being undertaken on a turn-key basis by a consortium involving Skanska International Civil Engineering AB and NCC International AB for the civil works, SWECO AB as the designer, ABB Generation AB for the electrical works and Kvaerner Boving Ltd for the mechanical works. Skanska and NCC have formed a subsidiary company for their joint undertaking called Uri Civil Contractor AB. Skanska is the leader of the consortium. The work was started in 1992 and the project is scheduled to be completed in May 1997. A general description of the project was provided by Heiner et al. in 1993

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