Study on Monitoring of Vacuum Preloading Process of Soft Soil Based on Electromechanical Impedance Technique

Recently, the study of soft soil foundation reinforcement using vacuum preloading technology has received widespread attention from scholars. Along with the emergence of numerous joint vacuum preloading treatment methods, the studies on the monitoring of the treatment process are relatively lacking. Therefore, this study adopts the electromechanical impedance (EMI) technique, with piezoelectric smart aggregates affixed to prefabricated vertical drains, to monitor and research the soft soil vacuum preloading treatment process through four sets of model barrel tests. During the tests, the piezoelectric coupling admittance of the structure is measured, and changes in the soil pore water pressure, shear strength, and moisture content are recorded. The analysis demonstrates that as the soil hardened, the resonant frequency of the admittance shifted toward an increasing frequency, and the peak admittance at the resonant frequency decreased. In addition, the degree of shift differs from layer to layer; the more pore water pressure dissipates, the greater the degree of shift. In addition, we calculate the root mean square deviation values from the admittance characteristic curves and fit them with the shear strength and moisture content to obtain function expressions, further confirming the correlation between the vacuum preloading process and admittance characteristics. The experimental results demonstrate that the EMI technique can effectively monitor the vacuum-preloading process.