Assessment of concrete dam foundation discharges for different reservoir levels following a hydromechanical discrete model

Abstract

The ability to anticipate and avoid failures in concrete dams necessarily includes a detailed analysis of the mechanical/hydraulic properties and monitoring data relating to the dam -foundation system, an in-depth analysis of the geometry of the foundation rock mass, complex numerical analysis of dam behaviour and quantitative interpretation models. This ability to assess the safety of the damfoundation system in an integrated way still needs to be improved, namely by incorporating coupled models that consider the significant interdependence between the mechanical and hydraulic behaviour. In addition, the models for interpreting hydraulic quantities are based on methodologies developed for the interpretation of the mechanical model, which, as a rule, do not fit the observed behaviour and do not consider the coupled behaviour. Coupled hydromechanical analysis of the water flow through the foundation rock mass of a concrete dam is carried using a 2D numerical model that allows seepage through the block interfaces and considers the influence of both grout and drainage curtains. Numerical predictions obtained during cycles of filling and emptying the reservoir are used to establish the influence lines of the hydrostatic p ressure on recorded discharges. Two different dam heights and two different foundation geometries are evaluated. Also, two different behaviour scenarios are assessed: i) linear elastic and ii) non -linear behaviour at the concrete/rock and rock/rock interfaces. A series of different polynomial curves are adjusted to the numerical predictions using the least square method to find the best fit equation which can later be adopted in the development of more accurate quantitative interpretation methodologies of recorded data.