Dynamic Mechanical Response Monitoring and Fatigue Life Assessment of Long‐Life Asphalt Pavement Based on Fiber Bragg Grating Sensor

Relying on actual engineering projects, this investigation carried out the application of fiber Bragg grating (FBG) sensors in monitoring the mechanical response of long‐life asphalt pavement structures and proposed a deployment scheme for FBG sensors to monitor the mechanical response of pavement structure. Combined with the deployment scheme, the survival rates of FBG sensors in the actual construction environments of the asphalt mixture surface layer, cement‐stabilized crushed stone base, and inorganic binding material‐stabilized soil base were counted. Finally, the evolution patterns of the field dynamic response and fatigue life of the surface layer, base layer, and subgrade under different vehicle axle loads, axle types, and speeds were analyzed by vehicle loading experiments. The results showed that under the actual working conditions of the pavement, the survival rate of the sensors was not high, and the survival rate of the surface layer sensors was the lowest. The activated FBG sensors had good cooperative deformation characteristics with the surface layer, base layer, and subgrade materials. This could realize the evaluation and analysis of the uniformity of the structural layer construction rolling process and the monitoring of the structural mechanical response of the pavement under dynamic loading. Under dynamic load, the longitudinal tensile strain of the asphalt mixture layer and the inorganic binding material stabilized layer bottom was larger than the transverse tensile strain. Both longitudinal and transverse tensile strains increased with the increase of load and decreased with the increase of vehicle speed. Therefore, the fatigue life of the surface layer and subgrade structure decreased with increasing load and increased with increasing speed, and the higher the test speed, the more significant the difference between the fatigue life under dynamic and static loads. When the load was higher, the soil pressure on the top surface of the subgrade was proportional to the vehicle speed, and the fatigue life of the subgrade decreased with the increase of speed. When the load was lower, the effect of vehicle speed on the top surface soil pressure of the subgrade was not significant, and the fatigue life of the subgrade basically remained stable.