*4.2. Settlement and Deformation Law*

Changes in the pore-water pressure caused changes in the shear strength. Figure 8 shows the deformation vector arrows of the subgrade protected by a capillary barrier. The subgrade with a capillary barrier was basically not affected by rainfall, while settlement still occurred. This was mainly because the slight change in the pore-water pressure at the bottom of the expressway shoulder slope caused the strength in the uplift area of the slip surface to decrease, which led to the shear deformation of the subgrade.

**Figure 8.** Deformation vector arrows of the subgrade with a capillary barrier.

Figure 9 shows the change trend in the expressway's pavement AB settlement with horizontal displacement. In the nonaffected area, the settlement of the conventional subgrade was relatively small, which was only 1 cm. While in the affected area, the settlement was large, which was up to 16 cm. Large different settlements occurred at the shoulder and in the subgrade. The different settlement was up to 15 cm. However, the subgrade using a capillary barrier had a ground settlement of approximately 1 cm in the affected zone and the noninfluenced zone. The different settlement was also relatively small. Surprisingly, even if the pore-water pressure in the subgrade did not change, the subgrade still had a certain amount of settlement. This was mainly caused by the shear deformation of the foundation.

**Figure 9.** Comparison of the settlement in the different subgrades.
