Comparison of Predicted and Measured Settlements of Reservoir Dikes on Lacustrine Clays

Brent Hay, Nelson Ferreira, James Blatz

In the proceedings of: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Dams and Embankments

ABSTRACT: Winnipeg is located in the glacial lake Agassiz basin which consists of highly plastic lacustrine clays overlying silt tills. Structures bearing on the lacustrine clays are typically subjected to long-term primary and secondary consolidation settlement. These consolidation settlements are a notable concern when considering the long-term design life of critical infrastructure. The Deacon Reservoir is located immediately east of the City of Winnipeg and provides fresh water from the Shoal Lake Aqueduct to the residents of Winnipeg. The facility contains four reservoirs (Cells); the first two were constructed between 1972 and 1978 with the subsequent two between 1996 and 1997. The perimeter clay dikes are approximately 6 m above surrounding prairie and consolidation since construction has resulted in a reduction of freeboard with time. Settlements between 160 mm and 450 mm have been measured and a total of approximately 675 mm are predicted, corresponding to roughly 100 mm to 500 mm of additional settlement. The results of a consolidation analysis which examine the historic and potential future settlements for the Cells are presented. The results of the analysis show good agreement between the settlement calculated using 1-Dimensional consolidation theory and measured data.

RÉSUMÉ: Winnipeg est situé dans le bassin du lac glaciaire Agassiz qui comprend de la till-silt sous-jacent aux lacustres argiles fortement plastique. Les plus grandes structures de terre tel que les digues portant sur la lacustre argile sont sujet au tassement de consolidation primaire et secondaire au fil du temps. Ces tassements de consolidation sont inquiétants quand on considère la performance et la vie utile à long terme de l™infrastructure essentielle. Le réservoir Deacon est situé immédiatement à l™est de la ville de Winnipeg et fourni de l™eau potable du aqueduc de Shoal Lake. Le réservoir Deacon comprend quatre réservoirs (cellules); les deux premiers ont été construits entre 1972 et 1978 et les deux derniers entre 1996 et 1997. Les digues d™argile du périmètre sont environ 6m au-dessus du sol encaissant et l™affaissement qui s™est produit depuis la construction se résulte dans une réduction de la revanche. Jusqu™à date des mesures entre 160mm et 450mm de l™affaissement sont consistants avec un total estimatif de 675mm de l™affaissement. Les résultats de l™analyse de consolidation qui ont examiné l™historique et le futur potentiel de l™affaissement pour les cellules sont présentées et comparées avec des affaissements mesurés plus de 30 ans suivant la construction. Les résultats de l™analyse démontrent une bonne entente entre l™affaissement estimé qui a été calculé en utilisant la théorie de consolidation unidimensionnelle et les données mesurées.

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Cite this article:
Brent Hay; Nelson Ferreira; James Blatz (2017) Comparison of Predicted and Measured Settlements of Reservoir Dikes on Lacustrine Clays in GEO2017. Ottawa, Ontario: Canadian Geotechnical Society.

@article{geo2017Paper762,author = Brent Hay; Nelson Ferreira; James Blatz,title = Comparison of Predicted and Measured Settlements of Reservoir Dikes on Lacustrine Clays,year = 2017}