Author(s): Mats Billstein; UrbaN. Svensson

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Abstract: The objective of' this study is to numerically evaluate if the Air Hypothesis is a potential explanation of the unusual pressure behaviour of the core at WAC Bennett Dam. Up to now. the pore pressures have exceeded the expected normal steady state distribution for about 25 years. The Air Hypothesis describes the influence of air bubbles on the pressure distribution in the core. An increased water pressure will compress the air bubbles and increases the amount of air that can go into solution at the upstream side of the core. At the downstream side, the situation is reversed, i.e. the air volume will increase and cause a hydraulic blockage. A one-dimensional numerical model, that is based on relevant conservation laws, physical laws (Darcy's, Boyle's, and Henry's laws) and the relationships between the relative hydraulic conductivity and water saturation level, is able to predict the pressure evolution in both a qualitative and quantitative way. The model is applied to both a hypothetical core and the core of WAC Bennett Dam. Results from a plug How analysis on the dissolution of the air in the hypothetical core are in fair agreement with the numerical results. Comparisons with pressure measurements from WAC Bennett Dam show that the Air Hypothesis is a potential explanation to the unusual pressure distribution in the core.

DOI: https://doi.org/10.1080/00221680209499906

Year: 2002