This paper describes the results of an investigation aimed at establishing whether pore fluids can affect cyclic behavior of fine-grained soils. The effects of pore fluids on the undrained cyclic behavior of artificial bentonite-sand mixtures and natural soils collected from the sliding surfaces of two earthquake-induced landslides, and their microstructures were studied by means of a ring-shear apparatus and a scanning electron microscope, respectively. The obtained results revealed that the presence of sodium chloride in certain concentrations in pore water would alter the particle arrangements, resulting in more open clay microfabrics, thus undermining the liquefaction resistance of soil. It was also demonstrated that in an acidic medium, the liquefaction potential of the studied soils increased.