Hydraulic conductivity and leachate removal rate of genetically different compacted clays

Abstract

Genetically different clays were compacted, contaminated and cured for 21 days with natural leachate from an old active waste disposal site and subsequently remolded at both West Africa (WA) and Modified AASHTO (MA) energies of compaction. The clays were thereafter investigated with a view to understanding the effect of contamination on hydraulic conductivity and mineralogy of the clays, soil-leachate interaction, influence of the energy of compaction and rate of leachate removal with time. Clay mineralogy revealed the presence of mixed clays including Anatase, Calcite, Hematite, Kaolinite, Quartz and Illite. The presence of these mixed clay minerals confers both attenuation and containment properties on the clays and, hence, makes the soils suitable for use as barriers in landfills. Hydraulic conductivity of the undisturbed and uncontaminated clays reduced with increase in energy of compaction from WA to MA. Leachate addition resulted in varied responses from the clays attributable to the different genealogy of the soils. Furthermore, the rate of leachate removal for the soils was observed to be 3.0 9 10 -3 cm/s for SMP 1, 4.0 9 10 -3 cm/s for SMP 2 and 8.0 9 10 -2 cm/s for SMP 5. These observations from the different soils are in agreement with results recorded in terms of consistency, hydraulic conductivity, mineralogy and compaction properties. However, influence of leachate on the structure of the genetically different soils played a contributory role in alteration of their mineralogy and, hence, their hydraulic conductivity.

Variations in geotechnical characteristics of some crude oil contaminated soils

“…Badv and Omidi (2007) explained that increase in permeability may be due to the contraction of double layer and increased pore spacing resulting from the adsorption of divalent cations into the soil matrix. Compaction of the soil may have engendered cracking of the weak substrate of the soil resulting in the formation of new macro pores with high permeability (Oyediran and Olalusi, 2017). Also, the dissolution of clay minerals in the soil by crude oil as the pore water is replaced by crude oil may also have led to increase in pore spaces, hence increase in The variation of Quartz and Kaolinite in the presence of crude oil in the soil resulted in an inverse relationship.…”

Untitled

“…As the moisture content of the smectite clay changes from dry to wet of optimum, some fabrics of the smectite clay particles tended to change from a flocculated to a dispersed arrangement because of compaction. Higher effective stress produced closer alignment of particles along the failure surface thereby, yielding a decrease in the voids that conducted flow thus, lowering the hydraulic conductivity at higher effective stress (Oyediran and Olalusi 2017). This smectite clay demonstrated a capacity to attenuate the movement of contaminants and prolong the release of a metal load-bearing contaminated water.…”

Assessment of the influence of copper and zinc on the microstructural parameters and hydraulic conductivity of bentonites on the basis of SEM tests

“…(2005), Meril (2014) and Dutta and Mishra (2016) believe that bentonite hydraulic conductivity increases with an increasing concentration of potentially toxic metals, such as Cu 2+ , Pb 2+ , Zn 2+ , in the solution. The authors (Arasan, 2010; Evangeline and John, 2010; Shariatmadari et al., 2011; Meril, 2014; Lu et al., 2015; Kobayashi et al., 2017; Oyediran and Olalusi, 2017; Li et al., 2019; Wang et al., 2019; Xu et al., 2019) agree as to the direction of changes in hydraulic conductivity of bentonites after exposure to landfill leachates, such as NaCl, KCl, CaCl 2 , MgCl 2 , ZnCl 2 , CuCl 2 , HCl, HNO3, NH 4 Cl, CH 3 COOH. Generally, the value of hydraulic conductivity increases.…”