## 3 Test Methods  
### Method Introduction  
In this study, field tests were performed to evaluate the performance of support and drainage conditions of pavement foundations. Laboratory soil index property tests were conducted on pavement foundation samples collected after drilling core holes. Table 1 summarizes the testing methods and corresponding test objectives. Field visual inspections, GPR, CHP, and DCP tests aimed at assessing the performance of the pavement foundation of the test sites. The GPR test is a nondestructive method commonly used to assess pavement thicknesses, determine locations of rebar, and identify defects such as voids within or beneath \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test Type** & **Test Name** & & **Test Objective** \\ \hline \multirow{8}{*}{Filed testing} & Field visual inspections & \(\bullet\) & Determine the extent and location of cracks and joint deterioration \\  & Ground Penetrating Radar (GPR) Scan & \(\bullet\) & Determine the surface thickness and rebar location \\  & Ground Penetrating Radar (GPR) Scan & \(\bullet\) & Locate possible cavities beneath the slabs \\  & Ground Penetrating Radar (GPR) Scan & \(\bullet\) & Determine the coring locations \\  & & Dynamic Cone Penetrometer (DCP) Test & \(\bullet\) & Evaluate the in-situ bearing capacity of pavement \\  & Dynamic Cone Penetrometer (DCP) Test & \(\bullet\) & foundation materials in terms of CBR \\  & Cone-Hole Permeameter (CHP) Test & \(\bullet\) & Evaluate in-situ hydraulic conductivity of pavement \\  & Core-Hole Permeameter (CHP) Test & \(\bullet\) & foundation materials \\  & Particle size analysis and Arterberg limits test & \(\bullet\) & Determine the soil index properties and Unified Soil \\  & Particle size analysis and Arterberg limits test & \(\bullet\) & Classification System (USCS) classifications of the pavement foundation materials \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The field-testing methods and corresponding objectives. Figure 2: Aerial images of six selected testing sections (The parts marked with red circles are the specific test sites). the pavement surface. In this study, a ground-coupled 1600 MHz antenna (model SIR-20, manufactured by GSSI) installed on a survey cart was used to collect three-dimensional (3D) information for the top 46 cm of the selected test sections, as shown in Figure 3.  
The DCP test was used to assess bearing capacity in terms of an empirically correlated CBR of pavement foundation materials. The test was performed in accordance with ASTM D6951 [43]. The test involves driving a conical point with a base diameter of 2 cm using an 8 kg hammer dropped at 57 cm. The penetration depth per blow was measured, which is referred to as the dynamic cone penetration index (DCPI). The DCPI was measured as follows for the various demonstration sections and used in the empirical correlations of Equations (1)-(3) to estimate the in situ CBR values. For all soils except CL soils with CBR < 10 and CH soils,  
\[\mathrm{DCP}\ -\ \mathrm{CBR}= \frac{292}{\mathrm{DCPI}\ \times\ 25.4^{1.12}} \tag{1}\]  
For CL soils with CBR < 10,  
\[\mathrm{DCP}\ -\ \mathrm{CBR}= \frac{1}{\mathrm{DCPI}\ \times\ 0.432283} \tag{2}\]  
For CH soils,  
\[\mathrm{DCP}\ -\ \mathrm{CBR}= \frac{1}{\mathrm{DCPI}\ \times\ 0.072923} \tag{3}\]  
The CHP test was performed to evaluate the drainage performance of the foundation materials. The test uses the falling head method to measure the in-situ permeability of the foundation layers after drilling cores, the corresponding test device as shown in Figure 4.  
In this testing methodology, a core hole with a diameter of 15 cm is bored through the pavement surface down to the underlying support layer. Subsequently, the testing apparatus is inserted into the borehole. To ensure an airtight seal within the interior of the core hole, an inflatable rubber tube is employed, inflated to an air pressure between 20 to 25 psi.