Verificação da eficácia dos sistemas de vedação e drenagem em fundações de barragens de concreto / Grouting and drainage curtains efficacy verification in concrete dam foundations

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

One of the biggest problems for hydraulic works safety is the uplift pressure. The execution of grouting, associated with drainage, is very important to control seepage through concrete dam foundations. Therefore, appropriate means to check the efficiency of those systems are essential for dam safety evaluation. Most of the uplift pressure criteria used nowadays for dam design is based on deterministic and empirical methods, originated from accumulated experience under certain specific conditions. When such criteria are used for a specific site, peculiar geological features may not be reflected in the data basis used as previous experience. Either unsafe or uneconomic designs may result from such practice. In this work, grouting and drainage systems effectiveness are evaluated in a probabilistic way, using statistical methods and data obtained during grouting execution, which provide good assessment for foundation properties variability. The first part of the research consisted, therefore, in the compilation and statistical distribution curves adjustment of data from Salto Caxias and Jordão river Hydroelectric Power Plants water pressure tests and grouting takes. The two dams are located in the state of Paraná, Brazil, and are owned by COPEL - Companhia Paranaense de Energia. They are founded on basaltic rocks, but have different permeability characteristics. Grout curtain effectiveness can be divided in two: in the grouting operation, with the treatment of cement grout take data, and in the curtain, which is measured by uplift and seepage reductions. Thus, by analyzing statistical distribution trends, it was possible to verify treatments effectiveness in the two dams. In the second part of the research, a probabilistic analysis methodology of drainage and grouting curtains effectiveness is proposed. This methodology is based on Monte Carlo method principles, randomly generating scenarios according to statistical distributions obtained in the first part of the work. By means of numerical simulations with finite elements, using foundation permeability coefficients following those statistical distributions, it was also possible to obtain a statistical distribution of uplift forces. Reliability analyses can be performed, and failure probabilities can be obtained using instrumentation readings, or even any uplift pressure criterion.

ASSUNTO(S)

drenagem reliability eficácia confiabilidade concrete dam foundation cortina de injeção subpressão método de monte carlo drainage efficacy fundação de barragem de concreto grout curtain uplift pressure monte carlo method

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