## 4 Results and Discussion
### Evaluation of pavement Foundation Drainage Performance
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test Site** & **Core Number** & **Test Location** & **K\({}_{\text{CHP}}\) (m/day)** \\ \hline \multirow{4}{*}{Site CRCP-23-A} & A1 & Regular & 0.52 \\  & A2 & Cracks & 8.44 \\  & A3 & Cracks & 0.31 \\  & A4 & Cracks & 17.34 \\ \hline \multirow{2}{*}{Site CRCP-23-B} & B1 & Cracks & 6.95 \\  & B4 & Regular & 4.05 \\ \hline \multirow{2}{*}{Site CRCP-12} & C4 & Regular & 3.44 \\  & D1 & Cracks & 0.58 \\  & D2 & Cracks & 2.59 \\ \hline \multirow{2}{*}{Site JPCP-4-A} & E1 & Regular & 0.24 \\  & E2 & Joint & 0.09 \\ \hline \multirow{2}{*}{Site JPCP-4-B} & F1 & Regular & 0.21 \\  & F2 & Cracks & 0.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: CHP test results of subgrade materials in each site. the corrosion of the rebar. The GPR survey, as illustrated in Figure 11b,d, indicates the potential existence of a predictable pattern in the occurrence of crack locations. The GPR results seem to indicate the formation of random cracks within the concrete slab, especially in areas between the rebars. This pattern suggests that the cracking might initiate at or near one of the rebars. The occurrence of cracks between the rebars could be attributed to stress concentrations or material defects due to rebar corrosion in these areas. Further investigation was conducted by drilling a core A3, from a transverse crack to determine if the crack originated from the rebar, as depicted in Figure 12a. The GPR result and field observations results show that two small transverse cracks propagated along the transverse rebars, also shown in Figure 12a,b. However, observation of core A3 shown in Figure 12c illustrates that the interface may not be the cracking initiation point. Instead, it may behave as a stress concentration area where the initiated cracks may follow the rebars to propagate. The DCP results shown in Figure 9 and CHP results shown in Table 3 illustrate the poor bearing capacity and drainage performance at site CRCP-23-A, which indicate that when the subgrade layer is not strong enough, lacking the necessary strength, it fails to adequately support vehicular loads. This could result in the formation of stress concentration areas in the areas around the rebars, leading to the development and propagation of cracks in these specific regions. Furthermore, at site CRCP-23-B, special attention was paid to the intersection of severe transverse and longitudinal cracks at core B3, as shown in Figure 13a,b. After drilling the core sample, an unexpectedly large gravel particle was found bene  
Figure 11: (**a**) Distresses observed at site CRCP-23-A, (**b**) GPR 2D scan result, (**c**) Magnified view of part of the distress, (**d**) GPR 2D scan result. Figure 12: (**a**) Schematic of crack locations, reinforced bars, and cores, (A2, A3, and A4 are the labels for the core sampling locations) (**b**) transverse cracks that developed along the transverse rebars, and (**c**) images of Core A3 at Site CRCP-23-A. in Figure 13c. It suggested a stress concentration area might have formed beneath the core B3 under the influence of vehicular loads. Additionally, the presence of the large gravel particle could have altered the direction of crack propagation, preventing it from following the path of the reinforcing bars.