Investigation of long term moisture changes in trackbeds using GPR

• A method in assessing the moisture content in trackbeds.
• Evaluation of long term moisture changes in trackbeds using GPR.
• Reflectivity of soil as a parameter to evaluate the condition of underground layers.

In the paper we proposed a method of assessing the moisture content in a subgrade that has been exposed to occasional rainfalls and seasonal weather effects. The method is based on obtaining and processing GPR data and allows investigating long term moisture changes in the railway trackbeds. The GPR waveform change is considered dependent on the attenuation of electromagnetic radiation in the medium and its reflection from the soil layer boundaries. To analyze the soil moisture content the integral reflectivity as a quantitative characteristic is used in this method. This variable is used to evaluate the moisture changes in soil under rainfalls and other seasonal factors. The method verification is performed using RAW data of GPR profiling of Tuapse–Adler (Russia) railway section in December 2009 and between May and September 2010. It's shown that the value of integral reflectivity is sensitive to the soil moisture. Thus the dynamic analysis of changes in soil moisture on the selected railway sections depending on the different seasons is made. These results are in good agreement with data obtained by a track recording car.