A Study on the Monitoring and Response Mechanism of Highway Subgrade Structures Based on Ultra-Weak FBG Sensing Array

The objective of this study is to overcome the technical limitations of conventional detection technologies in sensing dynamic stress and multi-physical field distributions. To this end, it proposes a novel approach to address the ambiguous damage evolution mechanism of multi-layer subgrade structures on expressways under dynamic load-temperature coupling effects. The establishment of a distributed sensing monitoring system based on ultraweak FBG Array, in conjunction with the design of a dual-grating sensing network for strain and temperature, has enabled the study to achieve high-precision monitoring of the entire strain field and temperature field of the subgrade structure. This system offers several advantages, including distributed measurement, long-term stable operation, and convenient installation. It effectively addresses the difficulties in achieving full-domain distributed monitoring and the life-span issues associated with traditional electrical sensors. Multi-parameter coupling analysis, which is based on dynamic loading tests and long-term monitoring data, revealed the dynamic response patterns of roadbed structures under the combined effects of modulus differences, burial depth effects, temperature gradients, and load parameters. This analysis verified the mechanical sensitivity of flexible subgrades and the mechanism of interlayer stress redistribution. The research findings provide innovative solutions for intelligent diagnosis throughout the entire lifecycle of highways, driving a technological leap toward real-time and comprehensive road health monitoring.