Seasonal Ground Freezing and Thawing Monitoring Using Piezoceramic Based Smart Aggregates

Abstract

Knowledge gained from frozen ground real-time monitoring is crucial in understanding the freeze/thaw status of the ground, which is important for applications such as construction and agriculture. The traditional monitoring of frozen ground is based on temperature measurement using thermocouples or other commercial tools. However, the inhomogeneous composition of the ground can cause uneven freezing and thawing across the field. In this paper, an active-sensing method was applied to quantitatively evaluate the soil freeze-thaw degree using piezoceramic based smart aggregate (SA) transducers. A pair of SAs with a pre-determined distance apart were embedded the soil specimen. One SA was used as an actuator to generate stress wave and the other one was used as a sensor to detect the propagated stress wave. The change of the mechanical properties of the soil greatly affected the SA-generated stress wave propagation through the soil during the freeze-thaw process. To quantitatively identify the soil freeze-thaw condition, a wavelet packet-based ground freeze-thaw indicator was applied to extract the degree of soil freeze-thaw condition.