A Comparative Study on the Hydraulic Conductivity of Sartigan’s Dam Till

Pierre-Alain Konrad, Jean Côté, Jean-Marie Konrad

In the proceedings of: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Earth Walls and Dams I

ABSTRACT: The hydraulic conductivity of the Sartigan dam foundation till has been studied both in situ and in the laboratory. The Sartigan dam is located in St-George de Beauce, on the Rivière Chaudière in the Province of Quebec. Three Casagrande piezometers were installed in a water drilled borehole for in situ permeability testing at depths of 6.5, 10 and in situ results were analysed using the Hvorslev method to establish the hydraulic conductivity, which ranged from 8 × 10-9 to 1 × 10-10 m/s. Sampling of the foundation was performed using a triple core drilling tool. The core samples were analysed with a computed axial tomography (CAT scan) in order to detect any defects due to sampling or the presence of large particles prior to the laboratory testing. Hydraulic conductivity testing was performed using a flexible wall permeameter on undisturbed samples as well as on reconstituted samples. The specimens had an average height and diameter of 25 mm and 80 mm. The hydraulic conductivity values of the undisturbed samples ranged from 2 × 10-9 to 2 × 10-10 m/s, while those of the reconstituted sample between 3 × 10-10 and 1× 10-10 m/s. The results obtained for both types of samples are in good agreement with the in situ measurements. This study therefore shows that testing on samples obtained from triple core drilling is reliable.

RÉSUMÉ: La conductivité hydraulique du till de fondation du barrage Sartigan a été étudiée sur le terrain et en laboratoire. Le barrage Sartigan est situé à St-George de Beauce, sur la rivière Chaudière dans la province de Québec. Trois piézomètres méabilité aux profondeurs de 6,5, 10 et 13 mètres. Les essais ont été réalisés à charge constante par le biais de burettes de situent entre 8 × 10-9 et 1 × 10-10 m/sobtenus ont été analysés au CAT scan dans le but de détecter des zones de remaniement et la présence de particules de grande dimension. Les essais de perméabilité en laboratoire ont été réalisés avec un perméamètre à paroi flexible sur des échantillons carottés et reconstitués. Les valeurs de conductivité hydraulique se situent entre 2 × 10-9 et 2 × 10-10 m/s. Les résultats obtenus en laboratoires concordent avec ceux obtenus sur le terrain. Cette étude montre donc que la

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