Research on Response Characteristics of GPR Method for Detecting Phreatic Lines in Embankments

The excessive elevation of the phreatic lines under continuous high-water levels is the cause of many dangerous situations in embankments. Therefore, accurately understanding the dynamic changes in the infiltration characteristics of embankments is of great significance for judging and evaluating the stability of engineering. This study conducted indoor model experiments and used ground penetrating radar to detect the phreatic lines of soil. By comparing the radar detection results with the measured position of the phreatic lines, it was determined that the phreatic lines appeared as a continuous strong reflection surface with similar shapes in the radargram, and the reflection below the reflection surface became weaker. Through time-domain analysis of the single waveform at different time points, it was found that the amplitude of the reflected wave at the saturation line was larger, and the energy attenuation below the saturation line was faster, resulting in a rapid decrease in amplitude; perform Fourier transform on a single channel signal to obtain a spectrogram, and perform frequency domain analysis on it. The main frequency is around 600MHz, and the second main frequency is around 900MHz. As the saturation line rises, the main frequency gradually shifts towards lower frequencies.