Hydromechanical Evaluation of Flow Behavior in Rock Foundations of Concrete Gravity Dams

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9610545 In the U. S. and world-wide, there are many existing dams that need to be inspected for potential deterioration of materials, to verify compliance with upgraded design requirements, or to respond to long term loss in performance or safety. In response to the increasing demand for electricity, new dams will be needed around the world. The foundations of large dams are key to the performance of the overall structure. Changes in stress levels (e.g. from changes in reservoir levels or temperature) can be responsible for changes in permeability due to joint opening and closure. Joint and rock mass permeability affects the magnitude and distribution of the uplift pressure at the foundation, as well as the efficiency of grout and drainage curtains. The uplift pressure, in turn, determines the stability of the dam against sliding. Thus, development of a realistic uplift pressure distribution is a significant consideration in the design of new dams and/or in the evaluation of existing dams to satisfy higher seismic or hydraulic design requirements. The research includes: 1) case studies of joint opening and closure under foundations of dams; 2) development of realistic uplift pressure distributions under flood conditions; 3) improvements in monitoring plans for dam foundations; 4) determinations of field-scale hydromechanical properties for the foundation rock mass and the dam/rock interface; 5) investigate the influence of factors such as dam geometry on dam performance and effectiveness of various remedial measures; and 6) improve understanding on the nature and basic characteristics of flow through jointed rock. ***