Concrete Gravity Dam Stress and Stability Evaluation
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Project Objective

This concrete gravity dam is approximately 77 feet high and 375 feet long and supports a reservoir that primarily serves the accompanying hydroelectric plant that supplies power to the nearby communities.

Geosyntec’s Scope of Services

Geosyntec performed a detailed stress and stability analysis of the concrete gravity dam, with the main objectives of: (i) evaluating stresses and factors of safety against instability under various loading conditions; (ii) developing threshold values and action levels for uplift pressures and piezometric water levels; (iii) identifying likely consequences to the dam stability, should these threshold values be exceeded; and (iv) developing recommendations and conclusions from the outcomes of the stress and stability analyses.

Geosyntec performed the following scope of services: (i) data reconnaissance, review, and evaluation of existing information; (ii) development and implementation of field investigation and laboratory testing programs; and (iii) engineering analysis and reporting. Geosyntec completed a comprehensive stress and stability analysis of the concrete and water barrier structures, including the spillway and non-overflow section. This analysis evaluates the safety of the water barrier structures for a wide range of loading conditions at multiple failure planes. The finite element method stress and stability analysis was used to determine if the sliding factor of safety (SFOS) requirements under probably maximum flood loading conditions were not met for the analyzed cross-sections, including the right non-overflow dam, the intake structure, and sections through the overflow spillway.

Notable Accomplishments

Geosyntec completed the project by designing post-tensioning ground anchors as a retrofit to increase the SFOS of the dam.