# Intelligent Compaction Measurement Value in Variability Control of Subgrade Compaction Quality
## 3 Methodology  
### Field Test of Continuous Compaction Control  
The test field was constructed in Zhejiang, China. Figure 1a shows the distribution of test points. The test field area is 600 m\({}^{2}\) (150 m \(\times\) 4 m), divided into two rectangular test zones with a width of about 2 m. There are 15 measure points which is 5 m apart on each side. A signpost is used on one side of the test strip to determine the test location.  
The construction type is soil-rock mixed subgrade with high-fill that is located in the cut to fill sections in the test field. As shown in Figure 1b, the acceleration sensor was fixed to a roller wheel to survey the vibration response to the subgrade. Prior to the compaction operation, a plan file that delineates the pavement edges can be loaded to the Compaction Information System (CIS) in order to be overlaid with the color-coded map [15]. It is shown in Figure 1c that the quality of subgrade compaction depends on the shade of the color. Figure 1d shows the compaction effect of cut to fill subgrade after completing one layer of subgrade compaction; the red line represents the boundary line of cut to fill subgrade. According to Test methods of soils for highway engineering [29], the soil is tested to determine basic physical parameters, including liquid-plastic limit, plastic index, optimum moisture content, maximum dry density, etc. Table 1 presents the test results [16].  
Vibration compaction is a process of interaction between material and compacting machinery. The roller response measurement value is called \(E_{vib}\), which is related to  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Maximum Dry** \\ **Density (g/cm\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Optimum** \\ **Moisture** \\ **Content (\%)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Liquid Limit** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Plastic Limit** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Plastic Index** \\ **(\%)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Particle** \\ **Content (\%)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Maximum** \\ **Particle** \\ **Diameter (mm)** \\ \end{tabular} } \\ \hline
2.12 & 11.2 & 30 & 23 & 7 & 59.6 & 304 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical parameters of subgrade soil.  
Figure 1: Layout of test field: (**a**) test zone; (**b**) installation position of acceleration sensor; (**c**) Compaction Information System (CIS) display at the operator station; (**d**) boundary line of cut to fill in the completion of roller compaction.  
the stiffness of compacted materials [17; 18]. Thus, vibration parameters of compacting machinery have a significant impact on the compacting effect. The single smooth drum vibratory roller (Liu Gong CLG1622E) was used in the field test. The roller's main technical parameters are shown in Table 2.  
For the research contents, five experimental conditions are set up in the test field to analyze the influence of compaction effect on different thickness of the filling layer (3)4(3) and strength of the underlying layer (1)2(3). Table 3 presents the parameters of 5 conditions.