## 3 Test Results and Analysis
### Thermal Strain Distribution of Pavement Model Test  
In this section, Fiber Bragg Grating (FBG) sensors in combination with strain gauges were utilized to collect strain data from the pavement model during the heating process in order to analyze the thermal strain distribution in the horizontal direction. The characteristics of the thermal strain distribution in the carbon fiber-heated pavement were also investigated.  
Figure 5(a),b show the trends in thermal strain with heating time for TS\({}_{\text{A}}\) and TS\({}_{\text{B}}\) at various depths of the pavement. The thermal strain on the pavement gradually increased as the heating duration increased. The rate of growth of thermal strain decreased with increasing vertical distance from the carbon fiber heating wire. The greatest thermal strains of TS\({}_{\text{A}}\) and TS\({}_{\text{B}}\), for example, were situated at a depth of 5 cm, 209 \(\mu\)e and 192 \(\mu\)e, respectively, and the minimum thermal strains were located at a depth of 15 cm, 86 \(\mu\)e and 80 \(\mu\)e, respectively. The thermal strain on the pavement near the carbon fiber heating wire is clearly of concern based on the foregoing properties.  
Figure 5(c) shows the consistency of the pavement's thermal strain in the horizontal plane at various depths. That is, the difference in thermal strain in the horizontal direction of the pavement between TS\({}_{\text{A}}\) and TS\({}_{\text{B}}\) at different depths. With increasing heating time, the horizontal thermal strain difference increased, then decreased, and ultimately stabilized. The horizontal thermal strain differential increased as heating time increased, followed by a pattern of decreasing and then stabilizing. Additionally, the trend became less pronounced the further the vertical distance from the carbon fiber heating wire. For example, after 1 h of heating beneath a 5 cm deep pavement, the difference between TS\({}_{\text{A}}\) and TS\({}_{\text{B}}\) reached a maximum value of 80 \(\mu\)e. With increased heating time, the difference between TS\({}_{\text{A}}\) and TS\({}_{\text{B}}\) gradually decreased and finally stabilized at 40 \(\mu\)e. And the gap between TS\({}_{\text{A}}\) and TS\({}_{\text{B}}\) was essentially constant at around 20 \(\mu\)e beneath 15 cm deep pavement. The above characteristics showed that as heating time and distance from the carbon fiber heating wire increased, the pavement thermal strain field became more stable.  
By comparing Figures 4 and 6, it is clear that the trends in pavement temperature change and thermal strain change were essentially the same during the carbon fiber heating pavement model process. Temperature and thermal strain variations with time were more visible at a depth of 5 cm for the carbon fiber heating hot line pavement layer. As a result, the linear correlation between TV\({}_{\text{A}}\) and TS\({}_{\text{A}}\) was fitted and examined under 5 cm depth pavement, as shown in Figure 7. TV\({}_{\text{A}}\) denotes the amount of TC\({}_{\text{A}}\) change. That is, the difference in temperature between the pavement and the starting temperature at various heating periods. The fitted curve's R\({}^{2}\) correlation value was 0.97. The thermal strain of carbon fiber-heated pavement could be observed to be primarily driven by the difference  
Figure 5: Trends of temperature gradients in horizontal direction and depth direction.