The effect of waste leachate on the dynamic parameters of clay soils

Leachate is a hazardous liquid that leads to numerous environmental problems. Soil pollution is one of the most important of these problems caused by poor leachate management facilities and limited land availability. Studies show that soil characteristics change during contamination, and these changes are a function of the type of soil and leachate. Therefore, it is necessary to evaluate the static and dynamic behavior of soils after contamination with leachate. Despite the importance of this issue, studies in this field are limited only to static behavior, and the effect of leachate on the dynamic behavior of soils remains almost unknown. Hence, an experimental effort has been made in this study to evaluate the effect of waste leachate sampled from the Alborz landfill on the dynamic parameters of three different clays under different overburden pressures (6.29, 18.88, and 31.47 kPa). For this purpose, the amount and type of heavy metals in the leachate were first determined using an inductively coupled plasma (ICP) spectrometer. Then, cylindrical soil samples were prepared in three different leachate contents (0%, 6%, and 12.5%) and subjected to a simple dynamic shear test. Moreover, the samples were photographed using an SEM microscope to investigate the effect of leachate on the soil texture. Based on the hysteresis loops obtained from simple shear tests and, subsequently, amounts of shear modulus (G) and damping ratio (D) calculated from them, it was found that pollution and its increase cause an increase in the shear modulus and a decrease in the damping ratio so that the growth of the shear modulus and the decrease in the damping ratio are affected by the type of soil and are more pronounced in soils with a lower paste range. It was also observed that the greatest effect of leachate on improving the shear modulus of the soil can be seen at lower levels of pollution. The increase in the influence of shear modulus and damping ratio of clay from overburden pressure was identified as one of the effects of soil contamination with leachate, which was more evident in clays with high paste range.