## 2 Field Test and Analysis
### Results Analysis of Field Test  
The horizontal displacements of section K12 + 850 under different construction periods as measured by CX1-1 and CX1-2 are shown in Figure 4. According to Figure 4, in an earlier stage of construction, horizontal displacement of the surface at the toe of the slope moves toward the embankment, while horizontal displacement of the deep shows lateral migration to the embankment. With the development of subgrade filling, both horizontal displacement of the surface at the toe of the slope and the deep show lateral migration to the embankment. The main reason for this is that the settlement of fill soil upside applies outward pressure on the soft soil in the lower part. At 5 m under the surface, which is the bottom of the deposit of the original river course and the top of the silt clay, the horizontal displacement achieves its maximum. This means that in the earlier stages, the filled soil is less influenced by extrusion than the soft soil in the lower part during construction, and the horizontal displacement monitoring at the top of the silt clay should be taken into account when soft soil is buried too deeply in the project. Meanwhile, under the silt clay, the horizontal displacement is smaller the deeper it gets. According to comparisons between CX1-1 and CX1-2, the horizontal displacement of the joint part of the road and embankment is smaller than that of the toe of the slope, meaning the new fill subgrade has little effect on the lateral deformation of the joint part of the road and embankment. At nearly 6 m height, which is the joint part of the new filled embankment and the slope of the old embankment, the horizontal displacement of the joint part of the road and embankment achieves its maximum, which means that lateral deformation easily mutates near the boundary of the soil, and a large lateral horizontal displacement can easily occur under the boundary. During filling, the rates \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Date**} & \multicolumn{3}{c}{**2010**} & \multicolumn{3}{c}{**2011**} \\ \cline{2-10}  & **11.20– 11.28** & **12.22– 1.22** & **1.25** & **2.21– 2.22** & **3.2** & **3.11– 3.12** & **3.20** & **4.23– 4.26** & **7.2– 10.15** & **11.25–** \\ \hline \multirow{3}{*}{Procedure} & Dredging and hydraulic fill & Fill sand and training band & hydraulic fill sand & hydraulic fill sand & hydraulic fill sand & hydraulic fill sand & hydraulic fill sand & hydraulic fill sand & hydraulic call & Fill time delay & Pixel \\  & sand & construction & 50 cm & 100 cm & 100 cm & 80 cm & 50 cm & 50 cm & 13.5 cm & 13.5 cm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Construction procedure of the test zone. Figure 2: Procedure of construction: (**a**) Mechanical dredging; (**b**) Backfill sand; (**c**) Plastic drainage board; (**d**) Geotextile laid; (**e**) Joining of new and old subgrades; (**f**) Geogrid laid; (**g**) Backfill clay; and (**h**) Pavement construction. The variation of settlement and embankment filling height of the K12 + 850 section in the field test up until 6 March 2012, is shown in Figure 5. As can be seen, the settlement of CJ1-1 is 1315.10 mm and CJ1-2 is 1295.97 mm. The settlement in February is nearly 30- 50 mm, much larger than 5 mm, and the settlement occurring every month is still very large. The final settlement of the embankment is predicted to be 1600 mm using the layer-wise summation method, so the settlement after construction is nearly 300 mm, and there is some redundancy of settlement. The degree of consolidation is nearly 80% and the consolidation is good, but there is a long time of preloading before unloading. Meanwhile, according to the curve, the rate of settlement is large during loading and gradually decreases during preloading or intermission of loading, so the rate of loading should be controlled to prevent the instability of the embankment from loading too fast.