Title

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

Translated Titles

Effects of Anisotropic Soil Hydraulic Conductivity on Slope Stability Using a Coupled Hydromechanical Framework

DOI

10.29417/JCSWC.201809_49(3).0004

Authors

蔡易縉(Yi-Jin Tsai);葉信富(Hsin-Fu Yeh)

Key Words

水力耦合模式 ; 水力傳導異向性 ; 降雨入滲 ; 邊坡穩定性 ; Coupled hydromechanical framework ; hydraulic conductivity anisotropy ; rainfall infiltration ; slope stability

PublicationName

中華水土保持學報

Volume or Term/Year and Month of Publication

49卷3期(2018 / 09 / 01)

Page #

167 - 177

Content Language

繁體中文

Chinese Abstract

在過去以數值模型分析降雨入滲對邊坡安全性之影響時,通常預設土壤水力傳導係數為均向,以簡化模式之分析,而忽略水力傳導異向性對邊坡穩定之影響。因此,本研究藉由暫態滲流分析及邊坡穩定分析建立水力耦合模式,探討水力傳導均向性改變對於邊坡不同位置處 (坡頂、斜坡、坡趾)之降雨入滲行為及邊坡穩定性之變化。研究中建立了不同土壤特性之邊坡以進行水力傳導異向性分析,透過研究結果,可瞭解當垂直向水力傳導係數不變時,水平向水力傳導係數提高 (異向性增加)造成降雨滲流越趨於水平往斜坡內部入滲,導致坡頂靠近斜坡處及斜坡位置之土壤更容易受降雨影響而安全係數下降。研究中以k_r描述土壤描述土壤異向性之大小,其為水平向水力傳導係數(k_x)與垂直向水力傳導係數(k_y)之比值(k_x / k_y),而研究結果顯示斜坡處受其影響最為顯著,k_r =1提高至k_r =100時,壤土、粉土及黏土邊坡斜坡處之濕潤帶分別向下加深23.3 %、33.3 %及50 %,而造成斜坡深處之土壤安全係數更快發生下降之現象。然而,對坡趾而言則呈現垂直向入滲速率趨緩而安全性得以維持之現象,以k_r = 1與k_r =100之含水量分析結果進行比較,壤土及粉土邊坡於坡趾處之濕潤帶厚度分別減少了23.3 %及30.0 %,而黏土邊坡則因透水能力極小而不受異向性改變之影響。由於水力傳導異向性對邊坡坡頂、斜坡及坡趾處受降雨之影響有明顯差異,因此建議未來進行降雨引致邊坡崩塌之研究時可將此因素納入考量。

English Abstract

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.

Topic Category 生物農學 > 農業
生物農學 > 森林
生物農學 > 畜牧
生物農學 > 漁業
生物農學 > 生物環境與多樣性
工程學 > 土木與建築工程
工程學 > 市政與環境工程