Carl E. Morris

Evaluation of numerical simulations of capillary barrier field tests

This paper presents a comparison of numerical simulations to the measured response of capillary barrier field tests. The simulations were of pilot-scale tests of four 7 m long, 1.2 m thick capillary barriers, two with 5% slopes and two with 10% slopes, with and without an included unsaturated drainage layers. The unsaturated drainage layer was included to encourage lateral drainage. The 5% sloped barriers were subjected to a period of constant infiltration for a period of 74 days, while the 10% system with the drainage layer had water added for 26 days and the conventional capillary barrier with a 10% slope was subjected to 43 days of infiltration. The numerical modelling was conducted using both drying and wetting soil moisture characteristic curves to determine their influence on the results. Differences between the field test and the model data were found, but in general the simulations appeared to adequately reproduce the response of the test systems. It was found that the use of wetting curve data provided a better fit to the field data, more accurately predicting the amount and timing of the percolate produced.

Moisture Removal from a Two-Layer Porous Media: A Conceptual Model and Experimental Results

Moisture removal from a two-layer porous media in which air is circulated through one layer and moisture is removed from the second has not been well studied due to the emphasis given to single-layer systems. This two-layer configuration is common in natural and engineered systems and can be used as a means to create a barrier to downward migrating fluids and to remove liquids and gases that may be present in the finer layer. However, there is little data on moisture removal from a two-layer porous media in which air is circulated through one layer parallel to the interface and moisture is removed from the finer second layer by evaporation. A conceptual model of the moisture removal from a two-layer porous media system was developed and compared to experimental moisture removal rates from laboratory scale dry barriers. The limited experimental data agrees well with the results predicted by the conceptual model, providing an initial validation.

Incorporating Near-Surface Processes in Modeling Moisture Movement in Soils

The movement of moisture into and through near-surface soils is of major importance in numerous areas of geotechnical and geoenvironmental engineering, impacting soil strength, contaminant transport, efficiency of waste containment systems, and slope stability. Numerical models are often used to simulate moisture movement and behavior of soil systems due to the cost, complexity, and time required to undertake field studies. However, these simulations often ignore or grossly simplify near-surface processes such as precipitation, snowmelt, run-off, and evapotranspiration. It is not uncommon to see complex systems simulated using a one-dimensional model in which the surface moisture flux for the site is represented by a steady-state infiltration rate that is based on the annual average precipitation. In this paper we examine the impact of incorporating non-steady state models for near surface processes such as evapotranspiration, precipitation, and surface runoff on simulations of soil moisture movement in capillary barrier systems. Simulations with and without transient near surface processes have been conducted for a variety of sites with different climates. These sites include a semi-arid climate, a site where the bulk of the precipitation occurs during the winter months, and a wet, humid climate where rainfall exceeds 2 meters per year. The results demonstrate that simplification or omission of near-surface processes can lead to erroneous results.