Effect of leachate and used motor oil on the geotechnical and mechanical characteristics of soils with different mineralogy under different moisture conditions

Abstract

ABSTRACT In order to evaluate the geotechnical characteristics of four types of fine-grained clayey soil, including clay with low plasticity (CL), calcium bentonite (CB), sodium bentonite (SB), and a mixture of 50% CL and 50% SB (CL-SB) from the effect of water, leachate and used motor oil (UMO) was used. Unconfined compressive strength (UCS), indirect tensile strength (ITS), standard compaction, Atterberg limit, and free swelling tests are performed. This results showed that the PI of SB, CB, CL, and CL-SB soils with leachate is 43, 25, 10, and 33% higher than water, respectively. The PI of SB, CB, CL, and CL-SB soils with UMO is 72, 66, 12, and 43% lower than water due to the low dielectric constant. Adding leachate compared to water caused a decrease in maximum dry density (MDD) for CL, CL-SB, SB, and CB by 2.6%, 4%, 6%, and 4.5%, respectively. Also, adding leachate and UMO reduces UCS and ITS of all soils. Due to SB soil’s high cation exchange capacity, the changes in its mechanical and geotechnical characteristics were higher than in other soils. Finally, the increase in soil moisture during the sample construction decreased the soil strength due to the addition of leachate and UMO.