Distributed pavement subgrade shape monitoring based on FBG sensing technique

It is often difficult to monitor the subgrade performance of an in service highway structure due to its depth and large in size. Traditional sensors for pavement performance monitoring are usually point-wise sensors and therefore cannot fulfill the requirement for large coverage. This paper introduces a shape measurement sensor based on Fiber Bragg Grating (FBG) sensing technique for pavement structure developed by our research group. It can provide large-scale layer shape measurement using only one FBG sensing element and can bear the high compaction force and high temperature during pavement construction. The proposed sensor has been test in lab to show high accuracy in measurement. In the construction of the He-da highway in Jilin province, the proposed sensor has been applied to monitor the subgrade performance for the first time. Ten sets of the sensors with individual length of about 15 m have been embedded and the performance data have been collected twice. The embedding process and monitoring data will be introduced and discussed. The results have shown the potential of the proposed sensor for future large scale application.