## 2 Field Test  
### Test Setup  
A part of Wansong East Road, which is located in Ruian City, China, was selected as the test site. The testing location is shown in Figure 1. The road was built over thick marine soft clay, which is characterized as having a high water content, high plasticity, high sensitivity, high compressibility, low shear strength, and low permeability [26; 27]. RDC on a soft clay embankment may increase the risk of excessive settlement and uneven settlement. There is a significant lack of data and engineering experience related to using RDC to improve soft clay embankment, so full-scale field tests are desirable for investigating the influence of the RDC on the soft clay embankment. The upper part of the embankment in the test section consisted of a fill layer with a thickness of 0.6 to 0.8 m of sandy gravel material. Underlying the fill, there was a natural, saturated soft clay with a thickness of 34 to 41 m. The particle size distributions and properties for each of these soils are presented in Figure 2, and Table 1.  
At the location shown in Figure 1, the length of the test section was 50 m, with a width of 10 m. Before the field test, preloading was done using a rolling machine with an excitation force greater than 30 tons to level the ground and improve trafficability prior to RDC. The response of the embankment under the influence of the 3 YCT32 16-t (each module being 8-t) three-sided impact roller was recorded under typical operating \begin{table}
\begin{tabular}{c c c} \hline \hline
**Soil Type** & **Index** & **Value** \\ \hline \multirow{8}{*}{Fill soil} & Natural moisture content: \% & 4.8 \\  & Volume moisture content: \% & 6.7 \\  & Optimum moisture content: \% & 10.2 \\  & Maximum dry density: g/cm\({}^{3}\) & 1.50 \\  & Unit weight: kN/m\({}^{3}\) & 16.5 \\  & Silt content: \% & 12.5 \\  & Natural moisture content: \% & 45.0 \\  & Volume moisture content: \% & 54.0 \\  & Liquid limit: \% & 50.2 \\  & Plastic limit: \% & 30.5 \\  & Unit weight: kN/m\({}^{3}\) & 17.9 \\  & Compression index & 0.48 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Material properties of soil. Figure 1: Overview of the field test site. Figure 2: Particle size distributions. conditions for the compaction of a controlled fill material (see Figure 3), which involves being drawn behind a tractor performing 40 passes and directed to travel at a speed of approximately 12 km/h. A monitoring section (see Figure 4) was set up in the test embankment to observe settlement, horizontal displacement, and pore water pressure (PWP). Settlement monitoring was carried out using the embedded settlement device (ESD) [28]. The ESD includes a liquid storage tank, settlement gauges (viz., datum point and measurement point), plastic pipe, and signal output cable, as shown in Figure 5. The settlement gauge consists of a vibrating-wire transducer and a cast iron tank [29]. When the ESD is in operation, the liquid-filled plastic pipe is connected to the settlement gauge at one end and to the atmosphere at the other. The ESD uses a vibrating-wire transducer to measure the surface pressure difference between the datum point and measurement point before and after the settlement, in order to determine their sedimentation value (accuracy of \(\pm\)0.05 mm). Three settlement gauges (measurement points) were buried at a depth of 0.25 m within the embankment fill material, as shown in Figure 6a. Figure 4: Sketch of monitoring section for test embankment. Figure 3: YCT32 16.5-ton three-sided impact roller. To monitor the horizontal displacement of the embankment, two in-place inclinometers (IPIs) [30; 31; 32; 33] were installed on both sides of the embankment. The composition of the instrument is shown in Figure 6b. Ten tilt accelerometers (with instrument spacing of 0.5 m) were mounted at 0 to 5 m depths below the ground surface along each IPI casing.