Ice structure monitoring with an optical fiber sensing system

Ice has been used as an effective and economical material for constructions of roads and platforms in cold regions. However, the practical applications of this brittle material are limited by the fact that ice structures can suddenly crack due to low tensile strength, be crushed due to excessive compression, melt and become soften as temperature elevates. In this paper, an early warning system is proposed to monitor the strain state and damage characteristic of ice structures. Firstly, both fiber Bragg grating (FBG) and Brillouin optical time domain analysis/reflectometry (BOTDA/R) sensors were installed in an ice block and an ice beam to understand their axial and flexural behaviors under a concentrated load. Secondly, the solution for strain state and damage process of ice structures was derived analytically under test conditions. Finally, an outdoor ice road test bed was built and continuously monitored for 34 h to validate the early warning system and understand the early stage behavior of ice structures. The experimental results agreed well with their corresponding theoretical predictions. The early warning system with optical sensors is effective and practical for long-term monitoring for ice structures.