## 6 Results and Discussion  
### Untreated Road Section  
Various approaches and load magnitudes are used in different parts of the world to codify traffic loads. In China, 20 kPa and 40 kPa are used for light and heavy traffic, respectively [58]. The same are used in this study to simulate the traffic loading. The final settlements are shown in Figures 15-17 at the unique nodes at traffic loadings of 20 kPa, 40 kPa, and 80 kPa, respectively; the settlement progressed in the first year and continued to increase to 3600 days with a slowing rate. Figure 15 depicts the final settlement after nine years of operation. The maximum value of the settlement at 20 kPa is approximately 1 mm, 2 mm, and 4.5 mm at the center, 1.2 m, and 2.4 m away from the center, respectively. Figure 16 shows the maximum value of the settlement in the road at 40 kPa, which is approximately 1.5 mm and 4.5 mm at the center of the existing road surface and 2.4 m away from the center, respectively. But, on the same load at the toe of the old road, the maximum settlement is 83% higher than the top center of the road, which shows that the subgrade settlement increases in the soil layer with increasing depth due to the location of the settlement point. Figure 17 illustrates that at the traffic load of 80 kPa, the final settlement on the surface of the road is 4.5 mm and 20 mm at the center and 4.7 m away  
Figure 14: Case setting (treatment strategies). (**a**) Case A: Geogrid at the base. (**b**) Case B: Geogrid at the base and CFG piles under new road embankment. (**c**) Case C: CFG piles under new road embankment and the joint. (**d**) Case D: Lightweight filling material as soil replacement. from the center, respectively. It is evident that the maximum settlement increases by 77% when the traffic load increases from 20 kPa to 80 kPa. Figure 16: Settlement on the pavement surface and toe for untreated embankment at 40 kPa. Figure 17: Settlement on the pavement surface for untreated embankment at 80 kPa. Figure 15: Settlement on the pavement surface for untreated embankment at 20 kPa. Figure 18 shows changes in the vertical displacement at the pavement surface at traffic loads of 20 kPa, 40 kPa, and 80 kPa. The graph shows that the widened portion of the road, under increasing traffic load, has exerted additional stresses on the foundation, which has increased the deformation characteristics of the road. It can also be noticed that the traffic load variations have a high effect on existing road settlement. It can be noticed that the final settlement is higher on the new road pavement surface than on the old road pavement surface. Also, the settlement of new roads has increased more rapidly at the junction of the old and new road pavement surfaces, and this is because of the fresh stresses developed at the joint due to the disturbance of the soil envelope at this location. Figure 18 shows that at 20 kPa, the maximum settlement is 10 mm, and at 40 kPa, the maximum settlement percentage increase is 23%. On the other hand, the maximum settlement at 80 kPa is 18.5 mm, which is 45% more than the maximum settlement at 20 kPa. It can be noticed that at 20 kPa, the settlement at the old road centerline is about 1.8 mm, and at the shoulder of the new road is about 8.5 mm, showing an uneven or differential settlement of 6.7 mm. Figure 19 shows the variation in differential settlement on the foundation surface at traffic loads of 20 kPa, 40 kPa, and 80 kPa. The trend in the settlement curves is like a trench, which shows that the settlement at the old road foundation is less than at the new road foundation. The settlement gradually increases until it attains a maximum value at the edge of the new shoulder. At 20 kPa, the final settlement on the surface of the foundation is approximately 6.5 mm, and with a 73% increase, the minimum settlement is 1.5 mm. At the traffic loads of 40 kPa and 80 kPa, the maximum settlement on the foundation of the existing embankment increases by 72% and 71%, respectively.