Is Your Concrete Dam Growing?

Acres has undertaken a number of projects to assess the present and future condition of concrete dams affected by alkali-aggregate reaction (AAR). AAR is a chemical reaction that occurs between reactive aggregates and the cement paste in concrete.

Acres is leading the way in the field of assessment of AAR-affected hydroelectric facilities. A sampling of recent projects includes the following:

  • Mactaquac generating station operated by NB Power, New Brunswick
  • Center Hill dam operated by the US Army Corps of Engineers, Nashville District
  • Seminoe arch dam operated by the United States Bureau of Reclamation, Denver

Mactaquac Generating Station

The 660-MW Mactaquac generating station sits on the Saint John River in the province of New Brunswick. Acres has been working with NB Power dealing with AAR and consequent expansion of the concrete structures including the powerhouse, intake, spillway and sluiceways.

Several innovative remedial measures have been undertaken to control the deformations caused by AAR. Numerous slots have been cut in the spillway, powerhouse, intake and penstocks. These slots have balanced the movements and improved alignment of the mechanical equipment. The response of these structures to slot cutting was analyzed in detail using the finite element program GROW3D. GROW3D was developed specifically for the analysis of AAR-affected hydraulic structures.

Other remedial measures at Mactaquac include installation of multi-strand tendons in the intake, grouting of intake and diversion sluiceway and installation of flexible couplings in the penstocks.

Center Hill Dam

Acres performed detailed stress analysis and structural assessments of the Center Hill Dam near Nashville Tennessee.

In this project, Acres performed a site inspection and review of historical data followed by a detailed GROW3D stress analysis of the dam and spillway. The finite element model was calibrated to field measured deformations and concrete stresses. The results of the analysis were used to provide an assessment of the dam and the need for remedial action.

Results from the GROW3D stress analysis are illustrated to the right.



Seminoe Arch Dam

The 90-m high Seminoe arch dam is located on the North Platte River near Rawlins, Wyoming. The dam was built in 1939 and signs of AAR were detected in the early 1950s. Acres was contacted by USBR to perform a GROW3D stress analysis of the dam and assess the need for further action.

The results of the analysis were used by USBR in a risk-based safety assessment of the dam. The GROW3D model provided an excellent match to measured displacements. The model also replicated the crack patterns observed on the downstream face of the dam. As a result of this work, recommendations were made for remediation.

For more information about AAR, contact Dan Curtis:
Tel: (905) 374-5200 x5243, Fax: (905) 374-1157, E-mail: dcurtis@acres.com
Visit our AAR web site at www.acres.com/aar