Application Of The Impedance Sensing Technology Of The Dual PZT In The Soil Freeze-Thaw Process Monitoring

Structural health monitoring based on the PZT patches has been used in various engineering fields. In this thesis, a novel embedded dual PZT is proposed. Besides, a new impedance measurement system is also designed for data measurement of the embedded dual PZT in the experiment. Based on the effective impedance method, the analytical models of the coupled vibration between the dual PZT and the host structure with different dimensions are derived. In the free vibration test of the dual PZT, the electromechanical impedance models of the piezoelectric ceramic with different dimensions were validated. And the 3D impedance analytical model of the dual PZT was further validated by embedding the dual PZT into the cement cubes.In the temperature sensitivity test of the embedded dual PZT, the dual PZT freely vibrated in an environment chamber, where the temperature sensitivity and piezoelectric effect of the dual PZT with the change of temperature is explored in this test. And on this basis this thesis explores the feasibility of electromechanical impedance(EMI) technology for the soil freeze-thaw state monitoring based on embedded dual PZT. Besides, the RMSD and CC indexes were introduced in the soil freeze-thaw process monitoring test as state change indexes.According to the theoretical and experimental research of this thesis, the following conclusions are able to be drawn:1. A new impedance measurement system is proposed in this paper, which has the advantages of wide frequency band, strong operability, short measurement time and high excitation voltage. This measurement system could make the reliable measurement of the PZT sensors realized.2. The impedance theoretical models of the dual PZT deduced in this thesis are correct. Besides, compared with the 1D and 2D impedance model, the 3D impedance model can effectively reflect the coupled vibration between the dual PZT and the host structure.3. The dual PZT maintains a stable piezoelectric effect with the change of temperature, which indicates that the new embedded dual PZT is insensitivity to temperature.4. The embedded dual PZT can be more precisely monitoring the soil state in the freezing and thawing process in the frequency band of 100kHz-500 kHz. In addition, the RMSD and CC indexes can be used as the index of the physical state change of the soil, and effectively reflect the state change of the soil in the freezing and thawing process.