The execution of grouting, associated with drainage, is very important for the control of seepage through concrete dam foundations. Most of the uplift pressure criteria used nowadays for dam design are based on methods, which are both deterministic and empirical, originated from accumulated experience under certain specific geological and geometrical conditions. When such criteria are used for a specific site, peculiar geological features may not be reflected on the data basis used as previous experience. In this work, grouting and drainage systems efficacy are evaluated in a probabilistic way, using statistical methods to analyze data obtained during grouting execution, which provide good assessment for the variability of foundation properties. A probabilistic analysis methodology is proposed, based on Monte Carlo Simulation principles, randomly generating hydraulic conductivity scenarios according to statistical distributions obtained from Lugeon tests carried out during site investigation. By means of finite element numerical simulations, adopting foundation permeability coefficients following those statistical distributions, it is possible to obtain a statistical distribution for uplift forces. Reliability analyses can be performed, and the probability of occurrence of any particular uplift force value can be assessed, such as values leading to failure, values predicted by any empirical criterion or even instrumentation readings.
After understanding the action of the uplift pressure under concrete dam foundations, at the end of the 19th century, the execution of grouting, associated with drainage, became rather important for the feasibility analyses of such works from both economic and safety standpoints. Consequently, many criteria for uplift pressure determination were established. In most cases, these methods are empirical and only rarely do they consider geological features of the specific site. Analyses with probabilistic methods are rare and hardly available in the literature.