Abstract
The Atterberg limits are essential information and the first step in soil classification for geotechnical purposes. Established laboratoryprocedures use distilled water in the plasticity and liquid limits determination. However, saline solutions frequently interact with soilsin the construction environment through fluid percolation processes. This work aims to understand the variation of the geotechnicalbehavior of two standard materials with different mineralogical compositions (kaolinitic and smectitic) when affected by NaCl ionicsolutions in different concentrations. The purpose is to simulate different soils in environments with the presence of saline solutions.This paper reports an experimental program in which a kaolinite-rich and a smectite-rich material received NaCl solutions in threedifferent concentrations (0.6 %, 3.5 %, and 15.0 %) and had their Atterberg limits determined under these conditions. Additionally,non-contaminated samples of both materials have had their limits measured using distilled water. Physical characterization testsincluded hygroscopic moisture, grain size distribution, grain density, plastic limit (PL), and liquid limit (LL). These data allowed thedetermination of the Skempton activity index (AI), plasticity index (PI), consistency index (CI), classification of soils in the UnifiedSoil Classification System (USCS), and in the Highway Research Board (HRB) with the group index (GI). Mineralogy was determinedby X-ray diffraction and physical chemistry by measuring pH in H2O and KCl, determining the ΔpH, the point of zero-charge (PZC),and the surface electrical potential (Ψo). The results show that the pH values rise with increasing salinity, while ΔpH, PZC, Ψo, LL,AI, PI, GI decrease with increasing salinity. The PL decreases with the increase in salinity for smectite and increases for kaolinite. TheUSCS and HRB demonstrate that the materials start to behave as fewer plastic materials with increased salinity. It is concluded that thevariations in the physicochemical parameters of the environment control and modify the geotechnical behavior of the fine-grained soils.
Highlights
The water content or humidity (h) is an essential parameter that controls behavior of fine-grained soils and affects their plasticity index (PI)
The saline intrusion process is a common mechanism in the supply of soluble salts in coastal areas, with relevant consequences for the soil-waterplant system (Alexakis et al 2015), and it impacts the behavior of soils for engineering purposes in foundation projects (Elsawy & Lakhouit 2020), earth dams (Mansouri et al 2017), liners for the containment of contaminants (Mishra et al 2009), and slope stability issues associated with loess soils (Xu et al 2020)
The materials used in this research are commercially available, the first composed of smectite and the second composed by kaolinite
Summary
The water content or humidity (h) is an essential parameter that controls behavior of fine-grained soils and affects their plasticity index (PI). The Unified Soil Classification System (USCS) recognizes water’s role and considers the Atterberg limits to classify silty and clayey soils. In the construction environment, the water that percolates in the soil can transport soluble salts, altering its geotechnical behavior. The saline intrusion process is a common mechanism in the supply of soluble salts in coastal areas, with relevant consequences for the soil-waterplant system (Alexakis et al 2015), and it impacts the behavior of soils for engineering purposes in foundation projects (Elsawy & Lakhouit 2020), earth dams (Mansouri et al 2017), liners for the containment of contaminants (Mishra et al 2009), and slope stability issues associated with loess soils (Xu et al 2020)
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