## 3 Analysis of Mechanical Response Index  
### Deflection Response Analysis  
The deflection values of the road surface were taken at 30 points for the three structures. The deflection of the road surface for the three structures is shown in Figure 2. The deflection values \begin{table}
\begin{tabular}{c c c c} \hline
**Layer** & **Structure I** & **Structure II** & **Structure III** \\ \hline \multirow{3}{*}{Surface} & 1800 & 1800 & 1800 \\  & / & / & 1600 \\  & 3500 & 3500 & 1500 \\ \hline \multirow{3}{*}{Base} & 6000 & 18,000 & 3600 \\  & 6000 & 3600 & 3600 \\  & 3600 & 350 & 3600 \\ \hline \multicolumn{2}{c}{Subgrade} & 45 \\ \hline \end{tabular}
\end{table} 
Table 2: Design parameters of pavement materials for each layer (unit: MPa). \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline
**Number** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** \\ \hline Coordinate/m & 0 & 0.0266 & 0.0533 & 0.0799 & 0.1065 & 0.1331 & 0.1598 & 0.1864 & 0.2130 & 0.2397 \\ \hline
**Number** & **11** & **12** & **13** & **14** & **15** & **16** & **17** & **18** & **19** & **20** \\ \hline Coordinate/m & 0.2663 & 0.2929 & 0.3195 & 0.3461 & 0.3728 & 0.3994 & 0.4260 & 0.4526 & 0.4793 & 0.6 \\ \hline
**Number** & **21** & **22** & **23** & **24** & **25** & **26** & **27** & **28** & **29** & **30** \\ \hline Coordinate/m & 0.9 & 1.2 & 1.5 & 1.8 & 2.1 & 2.4 & 2.7 & 3.0 & 3.3 & 3.6 \\ \hline \end{tabular}
\end{table} 
Table 3: Y-values of the selected calculation points of the pavement structure. Figure 3: _Cont._  
Under the uniform load of the double circle, the maximum compressive stress of the lower surface layer of structure I, II, and III was 0.2048 MPa, 0.2766 MPa, and 0.1524 MPa, respectively, with the order of structure II \(>\) structure I \(>\) structure III. The maximum tensile stress of the base layer was 0.0459 MPa, 0.1987 MPa, and 0.1072 MPa, respectively, with the order of structure II \(>\) structure I. The maximum tensile stress of the sub-base layer was 0.07510 MPa, 0.08095 MPa, and 0.07640 MPa, respectively, and the order was structure II \(>\) structure III \(>\) structure I. Under the uniform load of the single circle, the maximum compressive stress of the lower surface layer of structure I, II, and III was 0.261 MPa, 0.3436 MPa, and 0.2057 MPa, respectively, with the order of structure II \(>\) structure I \(>\) structure III. The maximum tensile stress of the base layer was 0.04860 MPa, 0.22610 MPa, and 0.11430 MPa, respectively, with the order of structure II \(>\) structure I. The maximum tensile stress of the sub-base layer was 0.07634 MPa, 0.08221 MPa, and 0.07710 MPa, respectively, with the order of structure II \(>\) structure III \(>\) structure I. Under the uniform load of single circle and double circles, the stress sequence of each key layer was the same. The lower surface layer was always subjected to compressive stress. Nevertheless, in the Specifications for Design of Highway Asphalt Pavement (JTG D50-2006), the fatigue cracking of the lower surface layer is controlled by tensile stress. Under the uniform load of the double circle and single circle, with an increase in distance, the stress of different layers was almost identical, indicating that the stress value at a distance could not serve as an evaluation index, and hence, the stress value after 2 m could be ignored. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Layer** & **Structure I** & **Structure II** & **Structure III** \\ \hline Lower surface layer bottom & \(-\)0.2048 & \(-\)0.2766 & \(-\)0.1524 \\ \hline Base layer bottom & 0.0459 & 0.1987 & 0.1072 \\ \hline Sub-base layer bottom & 0.0751 & 0.08095 & 0.0764 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Maximum tensile stress of key layers under the uniform load of double circle (unit: MPa).