Influence of organic pore fluid on geotechnical properties of soil.

摘要

According to the U.S. EPA, there are 488,496 confirmed cases of leaky underground storage tanks (UST) nationwide as of September 30, 2009. Soil contamination due to the oil spills and leaky USTs has a direct impact on the geotechnical properties of affected soil and, therefore, on already existing structures such as foundation embankments and clay liners. In addition, it has been a common practice to use contaminated soil as a fill material or roadway sub-base material. Therefore, it is necessary to investigate the effect of oil contamination on physical and mechanical properties of soil. Prior studies have shown the effect of pore fluid chemistry on the soil properties, such as permeability and shear strength. Dielectric constant and fluid viscosity have been found to have the major influence on soil behavior. However, the number of studies is very limited, especially when it is related to geotechnical properties of clays. Furthermore, the prior studies have been conducted with the assumption that the contaminant remains in the liquid state after its release into the soil. However, when contaminant is released into the soil, it can whether partition into the solid state and adsorb onto the soil particles or remain in the liquid state within the soil pores. The tendency of organic compound to partition into a solid or a liquid state during its release into the clayey soil may play a crucial role in geotechnical properties of contaminated soil. Liquid oil can act as a lubricant and impair the interlocking mechanism, while partitioned into the solid phase organic compound may have stabilizing effect by increasing friction between clay particles. The degree of adsorption of organic compounds onto the mineral surface can be estimated by the octanol-water partitioning coefficient. The current study examines the effect of gasoline on geotechnical properties of high-plasticity and low-plasticity clay. In addition, the effect of pore fluid properties, including dielectric constant and octanol-water partitioning coefficient, on the observed behavior of clay is studied in closer details. The study demonstrated that dielectric constant alone can't be attributed to the changes in geotechnical properties of soil. The adsorption process, however, was found to influence soil properties at lower concentrations of contaminant.