Effect of Different Non-aqueous Phase Liquids on Geoenvironmental Properties of Sandy Soils Stabilized with Bentonite

Energy requirements for remediation of petroleum-contaminated soils and strategy selection are essential from both environmental and geotechnical perspectives. The effectiveness of clay minerals and other stabilizers in enhancing the geotechnical properties of sandy soils contaminated with light non-aqueous phase liquids (LNAPLs) was confirmed in previous research. However, the combined impact of bentonite to sand ratio (BSR), and type and concentration of LNAPL simultaneously on geotechnical and environmental properties has not been thoroughly investigated and remains poorly understood. In this study, the influence of diesel and benzene with different concentrations (۱۰۰, ۱۵۰, ۲۰۰, and ۲۵۰ g LNAPLs/kg dry soil) on the geoenvironmental characteristics of sandy soils stabilized and improved using different BSRs (۰, ۰.۲, ۰.۴, and ۰.۶) were compereheslly evaluated. The results indicated an increase in maximum dry density (MDD) and a reduction in optimum moisture content (OMC) during the compaction tests. Additionally, a decrease in cohesion and a decrease in the friction angle were observed in soils with higher concentrations of LNAPLs and BSR, with diesel exhibiting more pronounced effects than benzene. An increase in MDD and a decrease in OMC were also noted with escalating concentrations of both LNAPLs. Based on the results, BSR = ۰.۴ was found to be the optimal value that the soil mixture exhibits high MDD, low permeability (۱×۱۰-۹–۷×۱۰-۹ cm/s), significantly increased cohesion (>۵۰ kPa), and acceptable internal friction angles (~۲۰–۲۲°), at the concentrations of ۱۵۰–۲۰۰ g/kg. Analytical techniques, including FTIR, EDAX, XRF, and XRD were confirmed these results, providing insights into the mechanisms of contaminant retention in bentonite-amended sandy soils. The findings of this study can inform the geotechnical design of structures on LNAPL-contaminated soils and guide the selection of appropriate remediation methods.

کلیدواژه ها:

Soil Microstructure Analysis ، Non-aqueous Phase Liquid Contamination ، Bentonite-Amended Sandy Soil ، Geoenvironmental Engineering ، Hydraulic and Shear Behavior