Geomechanical and structural analysis of contaminated residual granitic soils with gasoline

Abstract

Human activity brings several risks of contamination with pollutants of varying types and effects, with hydrocarbon compounds being of great concern as they are released by vehicles, industrial and construction activities and in areas with fuel reservoirs, among others. Hence, when these contaminants reach the soil, a legitimate question arises regarding their impact on the soil’s resistance characteristics. This work presents a case study of granite residual soils contaminated with gasoline under 8-, 16-, and 32-days, within index properties and geomechanical tests were analyzed to support remediation decision. CBR tests showed inconsistent results at shallow depths but a 16% capacity reduction beyond 12 mm with green gasoline. Direct shear tests showed similar friction angles but increased cohesion from particle aggregation, raising rupture stress by up to 68%. Oedometer tests showed greater deformability and lower yield stress, with compressibility coefficient around 0.133-0.161, in contaminated soils, aligning with large-deformation CBR trends. It seems that gasoline is a complex addition to the soil-water-air interaction, possibly transforming the soil into a hydro-phobic material and thus separating the water as the connecting agent, affecting the overall structure and support capacity of the soil. Future studies should focus on hydrocarbon percolation and leaching behavior in field conditions.