A PZT-Based Electromechanical Impedance Method for Monitoring the Soil Freeze⁻Thaw Process.

Jicheng Zhang,Jiahao Xiao,Chuan Zhang,Jinwei Jiang

doi:10.3390/s19051107

Abstract

It is important to conduct research on the soil freeze–thaw process because concurrent adverse effects always occur during this process and can cause serious damage to engineering structures. In this paper, the variation of the impedance signature and the stress wave signal at different temperatures was monitored by using Lead Zirconate Titanate (PZT) transducers through the electromechanical impedance (EMI) method and the active sensing method. Three piezoceramic-based smart aggregates were used in this research. Among them, two smart aggregates were used for the active sensing method, through which one works as an actuator to emit the stress wave signal and the other one works as a sensor to receive the signal. In addition, another smart aggregate was employed for the EMI testing, in which it serves as both an actuator and a receiver to monitor the impedance signature. The trend of the impedance signature with variation of the temperature during the soil freeze–thaw process was obtained. Moreover, the relationship between the energy index of the stress wave signal and the soil temperature was established based on wavelet packet energy analysis. The results demonstrate that the piezoceramic-based electromechanical impedance method is reliable for monitoring the soil freezing and thawing process.

Highlights

As one of the most important construction materials for engineering structures, soil is irreplaceable in civil engineering
Soon after the test started, the temperature of the about 20 °C and the lowest measured value was around −20 °C
Soon after the test started, the soil specimen began to decline sharply. It was almost 120 min before the temperature dropped to 0 ◦ C, temperature of the soil specimen began to decline sharply

Summary

Introduction

As one of the most important construction materials for engineering structures, soil is irreplaceable in civil engineering. In addition to earthquakes and soil erosion, soil expansion and contraction induced by the periodic freeze–thaw process is a cause of fatal damage to engineering structures such as roads, bridges, and buildings. The soil freezing and thawing process can cause soil expansion and contraction but can change the soil’s mechanical properties. Numerous studies about the influences of the freeze–thaw process on soil mechanical properties have been reported. Aldaood et al [1] demonstrated that the effect of freezing–thawing cycles on the durability of gypsum-containing soil is severe by comparing the uncompressed compressive strengths of gypsum soils with different gypsum contents under freezing–thawing cycles. Qi et al [2] analyzed the changes in the density, strength, and resilient modulus of Lanzhou loess soil under different freezing conditions

Methods

Results

Conclusion