Effects of Pore Fluids and Sand Particles on Electrochemical Characteristics of Sandy Soil Containing Soluble Sodium Salt

The electrochemical impedance spectroscopy (EIS) characteristics of sandy soil and pore fluids containing different concentrations of NaCl, Na2SO4 or NaHCO3 were tested and comprehensively analysed. The equivalent circuit fitting and analysis results show that the basic equivalent circuit of the sandy soil system is circuit (1) R(C(R(Q(RW))))). The EIS of different sandy soils show their respective characteristics. Compared with those of the pore fluids, the radius of the capacitive loop and the peak of phase angle for the sandy soil is small, showing the high corrosivity of sandy soil. The sand particles facilitate low-frequency processes and hinder high-frequency processes. In the high-frequency region, the three conductive paths in the sandy soil are mostly in the conducting state, and the corresponding modulus is large. At the frequencies of 10(0)similar to 10(2) Hz, the peak of phase angle for the sandy soil containing NaCl, Na2SO4 or NaHCO3 is greatly affected by the concentration of the pore fluid, which may be caused by the porous structure and the state of the "liquid bridge".