The frequency spectrum characteristics of unsaturated loess based on complex resistivity testing

The accuracy of the results is influenced by capacitive components. This paper focuses on loess in the Yichuan region and establishes the relationship between unsaturated loess matrix suction and complex resistivity parameters based on complex resistivity tests and soil-water characteristic determinations. It reveals the variation patterns of their spectral characteristics and derives formulas for loess saturation degree and complex resistivity. The research results indicate that the excitation frequency is negatively correlated with the amplitude and phase of complex resistivity. When the frequency is less than 1000 Hz, the amplitude and phase of loess complex resistivity fluctuate significantly, stabilizing gradually after it exceeds 1000 Hz. With the increase of matrix suction, the amplitude, real part resistivity, and imaginary part resistivity of loess gradually increase, with their correlation influenced by the applied frequency. Loess capacitance and dielectric constant decrease with the increasing matrix suction. A loess saturation degree-complex resistivity model is established using the real part resistivity and imaginary part resistivity, and the model can be used for monitoring moisture changes in loess. The research results provide new methods and perspectives for utilizing the frequency dispersion characteristics of loess in geological disaster monitoring.