Influence of pore-fluid salinity on the monotonic and cyclic behavior of Scheruhn kaolin

This article presents the results of an experimental program designed to evaluate the influence of pore-fluid salinity on the monotonic and cyclic behavior of Scheruhn kaolin. To achieve this, a series of experiments was conducted, varying both the salt type (solutions of sodium chloride, calcium chloride, sodium nitrate, and calcium nitrate) and their respective concentrations to induce different interparticle forces and soil structures. The testing program included oedometer compression tests, performed with loading applied either parallel or perpendicular to the consolidation direction, as well as undrained monotonic and cyclic triaxial tests with loading aligned to the consolidation direction. The experimental results revealed that an increase in electrolyte concentration led to a reduction in the void ratio and, consequently, a change in compression behavior. Both the compression and unloading coefficients decreased with increasing salt concentration. Additionally, under undrained monotonic loading, higher salt concentrations resulted in increased maximum deviatoric stresses. Under undrained cyclic conditions, the use of higher-molar saline solutions affected the inclination of the effective stress paths and the number of cycles the material could withstand before reaching failure conditions. The data were further analyzed from a microstructure perspective, incorporating soil structure observations obtained through scanning electron microscopy.