Geotechnical Assessment of Alameda Dam

Joseph Quinn, Bill Chin, Mark Pernito, Jody Scammell

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Infrastructure

ABSTRACT: Alameda Dam is a 42 m high and 1250 m long earthdam located in southeastern Saskatchewan. The dam is founded on 30 m of glacial till overlying high plasticity clay shale bedrock. During its construction , unexpected displacements occurred in the clay shale, which resulted in halting construction for 18 months to facilitate a review of the design. The dam was completed by adding stabilizing berms, and by constructing the remainder of the dam in controlled stages. In the spring of 2011, the reservoir was surcharged above its full supply level (FSL) of El. 562 m in order to decrease downstream flood flows resulting from high runoff. Concerns regarding the stability of the dam were raised when the displacements in the clay shale increased during reservoir surcharging. An interim stability analysis indicated that the factor of safety of the dam was significantly less than normally acceptable levels. In response to the concerns, the Water Security Agency expedited a comprehensive stability evaluation of the Alameda Dam, which consisted of additional site investigations, 2D and 3D limit equilibrium analyses, and advanced 2D and 3D deformation modeling (FLAC). This paper describes the assessment methodology, and presents the main results and conclusions of the stability evaluation.

RÉSUMÉ: -est de la province de la Saskatchewan. La fondation du barrage repose à 30 m dans le till glaciaire sus-jacent un soubassement de schistes cité elevée. Pendant sa construction dans les années 1990, des mouvements inattendus se sont de sa structure. Le barrage a été complété en y ajoutant des bermes de stabilité, et en construisant le reste du barrage par phases controlées. ire les crues en aval émanant des forts ruissellements. Des préoccupations ont été soulevées au sujet de la stabilité du barrage lorsque des mouvements du schiste argileux ont augmenté pendant la surcharge du réservoir. Une analyse intérimaire de la stabilité a indiqué que le coefficient de sécurité du barrage était considérablement inférieur aux niveaux acceptables. exhaustive de la stabilité du

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