A subgrade cracking monitoring sensor based on optical fiber sensing technique

The presence of cracks is ubiquitous and a major concern for subgrade. Effective detection and quantification of cracks in soil specimens or structures are the prerequisites for understanding the generation of cracks and their impacts. This paper introduces a cracking monitoring sensor for subgrade structure based on the Brillouin optical time domain analysis/reflectometry technique. The proposed sensor has been applied for the subgrade cracking monitoring of a test section of He-da highway in China. The total covering length of the installed sensors is more than 200 m. Sensor data have been collected four times within a freezing and thawing cycle between November 2015 and May 2016. The test results prove that the proposed sensor has high survival rate after installation and high accuracy in cracking detection and quantification. The field application demonstrates the feasibility of the proposed sensor in systematic performance monitoring of pavement structure.