以水力耦合模式評估土壤水力傳導異向性對邊坡穩定之研究

In studies on the effect of rainfall infiltration on slope stability, soil hydraulic conductivity has usually been assumed to be isotropic to simplify the analysis when using a numerical model; studies have ignored the influence of anisotropic hydraulic conductivity. Therefore, this study established a coupled hydromechanical framework using transient seepage and slope stability analyses to investigate the effects of changes in hydraulic conductivity isotropy on rainfall infiltration and slope safety at various locations (i.e., at the top of the slope, on the slope, and at the toe of the slope). The results showed that when the vertical hydraulic conductivity (k_y) was constant, increase in the horizontal to hydraulic conductivity (k_x) (an increase in anisotropy) caused the seepage of rainfall to tend to infiltrate into the interior of the slope. This resulted in the soil on top of the slope (near the slope) and on the slope being more easily influenced by rainfall, thereby leading to soil instability. The change on the slope was the most significant. When the anisotropic ratio k_r (= k_x/k_y) increased from 1 to 100, the wetting zones on the slopes of loam, silt, and clay deepened by 23.3%, 33.3%, and 50%, respectively. However, increased k_r led to a slower infiltration rate in the vertical direction at the toe of the slope. Comparing the results of k_r = 1 and k_r = 100, the thickness of the wetting zones at the toe of the slopes of loam and silt decreased by 23.3% and 30.0%, respectively. In the case of the clay slope, k_r changes did not reach significance because of its poor permeability. Therefore, this study suggests considering the effects of soil hydraulic conductivity anisotropy when estimating slope stability, to precisely determine the effect of rainfall on slopes.