A new TDR sensor for accurate freeze–thaw measurement

The variation of soil properties during freezing–thawing cycles, especially the reduction of subgrade strength during the thawing process, is the major cause of pavement damage in cold regions. This paper introduces the development and evaluation of an innovative guided electromagnetic (EM) wave [time domain reflectometry (TDR)] tube sensor to non-destructively monitor the freezing–thawing process. Experimental evaluation indicates that the sensor signals are responsive to the development of freezing–thawing. From the measured data, the degree of freezing–thawing can be accurately determined by the use of an empirical analysis algorithm. This paper demonstrates the capability of this new TDR sensor to non-destructively monitor the freezing–thawing status of soils. These will set the basis for a thorough investigation of the effects of freezing–thawing on soil behaviour, an important aspect for incorporating the seasonal effects on pavement design and preservation in cold regions.