*4.3. Variation Law of Safety Factor*

The safety factor can be used to reflect the possibility of slope instability to a certain extent. As the subgrade and foundation are influenced by rainfall, the pore-water pressure in the traditional subgrade decreased, which reduced the overall safety factor of the subgrade. The safety factor was reduced from 1.35 to 1.15 in one year as shown in Figure 10, and the decrease in the safety factor with time was nonlinear. The safety factor of the subgrade protected by the capillary barrier was almost unchanged. This was mainly due to the better blocking effect of the capillary barrier. In one year, the safety factor of the subgrade using a capillary barrier increased by 15% compared to the traditional subgrade.

**Figure 10.** Comparison of the safety factor in the different subgrades.

## **5. Conclusions**

In this study, we first proposed effective measures to block the infiltrating rainwater in the subgrade through a capillary barrier. Secondly, using the numerical simulation method, we conducted studies on the mechanism and stability of the capillary barrier used in the subgrade to control distress against wetting. The subgrade with a capillary barrier could effectively use the different permeability coefficients of the different types of soil to achieve an anti-seepage effect, which minimized the deformation of the subgrade and increased stability. Using the numerical simulation method, this paper analyzed the pore-water pressure distribution, settlement, and safety factor of the conventional subgrade and the subgrade protected by the capillary barrier. Through a comparison of the numerical results of the two subgrades, the following conclusions were drawn:

