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Limits of the geological predictions constructing the samanalawewa pressure tunnel, Sri Lanka

Limites des prévisions géologiques dans la construction d'un tunnel sous pression au barrage de samanalawewa, Sri Lanka

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Abstract

The Samanalawewa Hydroelectric Power Plant in Sri Lanka consists out of a 110 m high dam, 5.5 km near surface pressure tunnel and a powerhouse equipped with two Francis turbines of 62 MW each.

To explore the geological conditions for the pressure tunnel about 6500 m were drilled with a total of 97 boreholes. Additionally surface investigations and a geophysical program were realized in order to optimize the drilling campaign.

Notwithstanding this very extensive field investigations important modifications in the design of the tunnel had to be made during construction. Consequently, the contractor claimed additional not foreseeable construction works.

At least the question of the possible precision of geological prediction within reasonable economical limits had to be answered.

Résumé

Au Sri Lanka, la centrale hydroélectrique de Samanalawewa est constituée par un barrage de 110 m de haut, un tunnel sous pression, près de la surface du sol, d'une longueur de 5,5 km et une usine équipée, de deux turbines Francis, ayant chacune une puissance de 62 MW.

Afin d'examiner les conditions géologiques du tunnel sous pression, l'on fait sur 6 500 m un total de 97 forages. Par ailleurs, des recherches à la surface et un programme géophysique ont été réalisés afin d'obtenir une campagne de forages optimum.

Cependant, malgré ces recherches très poussées, d'importantes modifications du tracé du tunnel ont dû être faites lors de la construction. Aussi donc, l'entrepreneur exigera des travaux supplémentaires non prévus.

Enfin, la question concernant la prédiction géologique la plus précise possible dans des limites économiques acceptables a été élucidée.

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Authors and Affiliations

  1. Electrowatt Engineering Services Ltd., Bellerivestrasse 36, 8034, Zurich, Switzerland

    Karl-Heinz Nagel

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  1. Karl-Heinz Nagel
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Nagel, KH. Limits of the geological predictions constructing the samanalawewa pressure tunnel, Sri Lanka. Bulletin of the International Association of Engineering Geology 45, 97–110 (1992). https://doi.org/10.1007/BF02594909

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