本研究利用FLAC程式，對水平地表與斜坡上之基礎承載行為進行數值模擬。主要目的在於探討坡角10°、20°與30°下，斜坡折減效應對承載力之影響，並提出斜坡承載因子與折減因子之設計圖表以供參考使用。斜坡折減因子之觀念是以水平地表承載力作為基準值，對斜坡承載力進行正規化而獲得。 數值分析之主要參數為：斜坡方面包含斜坡高度與坡角；基礎配置方面包含基礎位置與埋置深度；土壤材料參數方面包含摩擦角、剪脹角與凝聚力。在不同坡角下搭配各參數作一系列探討，以了解各參數對斜坡折減效應之影響。 當基礎置於坡頂處，承載力隨著斜坡高度增大而遞減。高度大於臨界斜坡高度Hcr時，折減效應完全發揮，承載力減至最小且維持定值。基礎位置方面，折減因子隨著基礎距斜坡愈遠而遞增。而隨著坡角與摩擦角增大，基礎與坡頂之臨界距離De(cr)遞增。以上之趨勢主要受到坡角與摩擦角影響，而剪脹角之影響較不顯著。 In this study, FLAC is applied to numerically simulate the behavior of foundation bearing mechanism over horizontal ground and slope. The effect of reduced bearing capacity due to slope is analyzed with slope angles of 10°, 20°, and 30°. Design chart with bearing capacity factors and reducing factor for slope is introduced for applications. The concept of reducing factor is to normalize the bearing capacity factors for horizontal ground with those for slope. The parameters for numerical analysis are: height and slope angle for slopes; position and embedded depth for foundations; friction angle, dilation angle and cohesion for soil material properties. Combinations of parameters under different slope angles are studied to evaluate the effect of reducing factor. When a foundation is placed on the edge of a slope, bearing capacity decreases with slope height increases till critical height (Hcr) is reached. Under this circumstance, the effect of reduced bearing capacity due to slope is maximized and the bearing capacity retains a constant no matter how the height of slope increases beyond Hcr . For the effect of foundation relative position, the reducing factors, αγs, αcs and αqs increase with the increasing of distance between edge of a slope and foundation . The critical distance, beyond which the slope effect no longer exists, increases with the increasing of friction angle and slope angle. Above relationships are mainly affected by slope angle and friction angle, but not obvious by dilation angle.