Investigating the effect of gasoline on the shear modulus of sandy soils using a bender element device

Determining the shear modulus of the maximum small strain of contaminated soils is of particular importance and is one of the most basic soil properties in earthquake and dynamic loads. Accordingly, the present study aims at investigating the long-term and short-term effects of hydrocarbon pollution on the maximum shear modulus (G(max)) since the two types of sands are standard Ottawa and poorly graded sand (SP) from the Ilam-Iran petrochemical plant. In this sense, a sequence of bender element experiments was performed on the clean and contaminated sand samples under the same conditions in order to investigate the effect of gasoline pollution on G(max) in short-term and long-term conditions. The results show that, regarding the short-term analysis, the G(max) value of SP sand was more sensitive than that of standard Ottawa sand. Moreover, increasing hydrocarbon up to 4wt.% in both types of sand significantly increases G(max), and increasing it further would reduce G(max). Furthermore, according to the experiments, adding more than 8wt.% of hydrocarbon in both types of sand has no effect on G(max) changes. On the contrary, regarding the long-term analysis, the effects of the weathering process can clearly increase the G(max) of both types of sand, so that the changes in shear modulus are greater in the first six months. Significantly, most of these changes occur in the first two months. Contrary to the results of short-term analysis, when Ottawa sand samples are contaminated, they become more sensitive to the process of weathering whose effect on G(max) at 4wt.% contaminated samples of both sands is more noticeable, as compared to species containing 8 and 12wt.%

Automated summary

Determining the shear modulus of contaminated soils is crucial in earthquake and dynamic load analysis. This study investigates the effects of hydrocarbon pollution on the maximum shear modulus of two types of sands. The results show that short-term analysis indicates greater sensitivity of poorly graded sand to pollution, while long-term analysis reveals the significant impact of weathering on both types of sands.