117-29 Relating the Air Permeability of Mayon Sand with Its Soil-Water Retention Curve: Measurements and Modeling.



Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

Augustus C. Resurreccion, Institute of Civil Engineering, University of the Philippines, Quezon City, Philippines, Per Moldrup, Aalborg Univ Sohngaardsholmsvej 57 D-building, Aalborg University, Aalborg, DENMARK, Ken Kawamoto, Saitama University, Saitama, JAPAN and Toshiko Komatsu, Saitama University, Saitama, , JAPAN
Air permeability (ka) and soil-water retention curve are two important parameters that are needed when simulating the movement of volatile organic chemicals in the subsurface. In this study, we measured the air permeability and soil-water retention curve of sand obtained within the vicinity of Mayon Volcano in the Philippines, across a wide range of matric potentials (ψ) and soil-water contents.  Samples were prepared (1) by adding a pre-determined amount of water to sand, left to equilibrate in a sealed bag, and repacked at a bulk density of 1.5 g/cm3 for air permeability; or (2) by saturating repacked 1.5 g/cm3 sands and draining to a desired matric potential in a sandbox or a pressure plate apparatus for the soil-water retention curve. In addition, independent data sets of air permeability where obtained on 1.5 g/cm3 sand samples drained to different matric potentials. The variation of ka with soil-air content (ε) showed an increase in ka during the drainage of the bigger pores (effective diameter >  0.03 mm) while no further significant increase in air permeability when effective pore size of less than 0.03 mm has been drained. A power law ka(ε) model was fitted into the ka(ε) data for ψ ≥ -100 cm H2O (pF 2 where pF = log(-ψ; in cm H2O) while a constant value described the ka(ε) in the dry region where ψ < -100 cm H2O. A ka(pF) model was developed by combining the developed ka(ε) model with the van Genuchten soil-water retention model and tested on the independent ka(pF) data sets. The developed model reasonably captured the behavior of the air permeability as a function of matric potential.  
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See more from this Session: General Soil Physics: II (Includes Graduate Student Competition)