Development and application of new FBG mini tension link transducers for monitoring dynamic response of a flexible barrier under impact loads

Flexible barriers, as an effective protective measure to mitigate landslide hazards, have attracted a lot of interest from the geotechnical community. The dynamic response of flexible barriers subjected to impact loads is of great concern. However, the forces developed on ring-net barriers during impacts have not been effectively measured and the dynamic behavior of barriers has not been fully understood. In this study, new mini tension link transducers based on fiber Bragg grating (FBG) sensing technology are uniquely developed to both link adjacent rings of a flexible barrier and measure the forces between rings. Besides, a novel monitoring system based on the new FBG mini tension link transducers is established for detecting dynamic response of a flexible barrier under impact loads. Calibration results of the FBG mini tension link transducers demonstrate that the wavelength shift of the FBG sensor has a linear relationship with the applied force with high accuracy. A single boulder impact test and a debris flow impact test were conducted to investigate the performance of the FBG-based system. The results reveal that the FBG mini tension link transducers are capable of capturing the evolution of the forces between rings of the flexible barrier, and the FBG-based system can be used for monitoring the dynamic response of the flexible barrier under impact loads.