Time domain reflectometry sensor-assisted freeze/thaw analysis in geomaterials

Freeze–thaw is a major source of damages and deteriorations for infrastructures in cold regions. Most of the existing investigations focus on soil behaviours in the completely frozen or completely thawed state. Tools to assist the determination of freeze/thaw status and its effects on geomaterials including soils are currently rare. This paper firstly introduced the design of an innovative guided electromagnetic wave sensor called Time Domain Reflectometry (TDR) tube that can non-destructively monitor the freeze/thaw process in standard sized soil specimens. An analysis algorithm was presented for interpreting TDR signals accordingly to determine the degree of freeze/thaw. The determined freeze/thaw statuses were then compared with deformation moduli obtained with compression test. An empirical relationship for freeze–thaw status-dependent mechanical properties was proposed based on the experimental observation. On the other hand, a framework of sensor-assisted analysis of freeze/thaw effects on soils was established. The framework concentrates on mechanical behaviours including stresses and deformations which are responsible for the distresses in the infrastructures. Poroelastic relationships, macro–micro relationship and the thermal dynamic equilibriums between phases were incorporated to obtain a close form solution for the simulation model. A simple case study was conducted to demonstrate the fusion of sensor data and computational simulation to investigate the freeze/thaw effects on soils.

► TDR as a tool in freeze/thaw analyses is explored and tested.
► The concept of sensor-assisted analysis is realized with a theoretical framework.
► Continuum mechanics, thermal dynamics, macro–micro relationships are included.
► Real-time monitoring with a TDR sensor is combined with theoretical formulation.
► The application potential is investigated with a simplified model in a case study.