Browsing by Author "Dawson, C."

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    How to Relate Monitoring Well and Aquifer Solute Concentrations
    (1992-10) Chiang, C.; Raven, G.; Dawson, C.
    Field data show disparities between organic solute concentration in the aquifer and that in monitoring wells; an order of magnitude disparity has been recorded in some cases. Therefore, it is important to be able to relate concentrations between the two media for design of remediation systems. More significantly, to assess the impact of the leachate from a landfill on a downgradient drinking water well, it is important to correlate aquifer concentration with that in a drinking water well such that the true risk is not overly estimated. A three-dimensional finite difference flow and transport model applied to demonstrate the disparity between aquifer and well concentrations is indeed well founded and can be quantified. The modeling shows that the concentration in the well is a function of the initial vertical concentration profile in the aquifer, the amount of flux from below the partially penetrated well, the degree of penetration, the soil lithology, and the amount of purged water before sampling. Based on these parameters, an approximate analytical solution is developed that agrees well with numerical solutions.
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    Numerical Techniques for the Treatment of Quasistatic Solid Viscoelastic Stress Problems
    (1993-01) Shaw, S.; Warby, M.K.; Whiteman, J.R.; Dawson, C.; Wheeler, M.F.
    For quasistatic stress problems two alternative constitutive relationships expressing the stress in a linear viscoelastic solid body as a linear functional of the strain are derived. In conjunction with the equations of equilibrium these form the mathematical models for the stress problems. These models are first discretized in the space domain using a finite element method and semi-discrete error estimates are presented corresponding to each constitutive relationship. Through the use respectively of quadrature rules and finite difference replacements each semi-discrete scheme is fully discretized into the time domain so that two practical algorithms suitable for the numerical stress analysis of linear viscoelastic solids are produced. The semi-discretes estimates are then also extended into the time domain to give spatially H1 error estimates for each alogrithm. The numerical schemes are predicated on exact analytical solutions for a simple model problem, and finally on design data for a real polymerical material.