地下水水位變化對於邊坡穩定扮演重要影響角色。藉由序率方法產生設定模式輸入值變異(如土壤異質性)量化模式輸出不確定性(如邊坡位移量)。本研究目的為探討材料水力傳導係數、孔隙率與材料單位重等參數計算邊坡穩定的不確定性分析。本研究採用逐步高斯模擬法 (Sequential Gaussian Simulation), 產生隨機水力傳導係數、孔隙率、與材料單位重隨機場，並使用商業軟體FLAC3D (Fast Lagrangian Analysis of Continua in Three Dimensions) 模擬穩態地下水流場。模式固定幾何形狀與邊界條件，量化穩態流場與邊坡位移量不確定分析。模擬結果顯示水力傳導係數對於地下水位具有顯著影響。依據本研究設定之背景流場梯度，壓力水頭與地下水位變異數相較水力傳導係數具有小於1至2個數量級。在下游邊界附近具有較高壓力水頭變異，並且導致邊坡穩度較高不確定性。另外，本研究也探討孔隙率與材料單位重對於邊坡位移不確定性影響，材料單位重空間變化對於邊坡位移不確定相較於孔隙率影響較大。;Previous investigations have recognized the important role of groundwater variations on slope stability. Stochastic approaches are useful techniques to quantify the input uncertainty (i.e., the soil heterogeneity) on the output uncertainty (i.e., the displacement uncertainty). This study aims to develop a stochastic modeling workflow based on numerical Monte Carlo simulations. The Monte Carlo simulations involve a number of procedures including simulations of random hydraulic conductivity fields, random porosity fields, random unit weight fields. This study employs sequential Gaussian simulation method (SGSIM) model to generate random realizations of hydraulic conductivity fields, porosity fields, and unit weight fields. The commercial model FLAC3D (Fast Lagrangian Analysis of Continua in Three Dimensions) is then used for the simulations of slope stability. By collecting realizations of flow and displacement solutions in a slope with a fixed geometry and boundary conditions, the workflow can quantify the propagation of flow uncertainty on displacement uncertainty. The simulation results show that the variance of the logarithm of hydraulic conductivity significantly influences the water level variation in the slope system. The pressure head and values of water level variance values show one to two orders of magnitudes smaller than that of the logarithm of hydraulic conductivity, depending on the background flow gradients. The high-pressure head variance occurs near the downstream boundary. These high-pressure head variances also lead to high instability in the slope system. In addition, this study also discusses the influence of spatially variable porosity and unit weight parameters on the displacement uncertainty. Although the flow pattern is similar to homogeneous cases, the displacement uncertainty induced by porosity variation is relatively small as compared with the displacement uncertainty induced by spatial variation of unit weight.
