Burland(1987)提出的大地工程分析金三角可將大地工程分析不確定性分成地質模型、地盤模型與大地工程模型三種模型。地質模型包含研究區域本身的各項地質特徵，如傾角、地下水分布及水壓與地層介面等。地盤模型是以地質模型為基礎，加入各項試驗取得的大地工程參數，如凝聚力與摩擦角等。大地工程模型則是在地盤模型中依據穩定或分析需求，並搭配合理的假設下選擇相關的模型進行分析，如邊坡穩定極限平衡公式與數值軟體模型等。 本研究以上述三種模型中的地質模型不確定性作為主要討論方向，探討邊坡穩定性受不同滑動面傾角來源與滑動面上之臨界地下水壓不確定性之影響，邊坡穩定之平面破壞模式假設為三類，分別為邊坡中之鋼軌樁正常作用、邊坡中之鋼軌樁鏽蝕破壞以及邊坡中之鋼軌樁前產生張力裂縫三種破壞模式。在上述三種破壞模式下，分別探討傾角與地下水壓不確定性在不同組合下之破壞機率，並以破壞機率對邊坡穩定的影響作敏感性分析。 研究成果顯示，乾燥邊坡的破壞機率隨傾角變異係數增加而增加，不同破壞模式之中，鋼軌樁前產生張力裂縫發生平面破壞之破壞機率最大，與現地調查觀察到的籃球場潛在裂縫相符合。考慮滑動面上有臨界地下水壓作用時，在不考慮傾角變異係數的大小時，整體分析結果以傾角變異性對破壞機率的敏感度較地下水壓變異性高。本研究也以三維數值模型探討弱面凝聚力與摩擦角具不同強度下之組合對校區整體崩滑與運移堆積狀況之影響。結果顯示，在目前狀況下整體校區是相當穩定的。 ;According to Burland (1987), the uncertainty of geotechnical analysis can be divided into three types of models: Geologic model, Ground model and Geotechnical model. The geologic model includes various geological characteristics of the study area, such as dip angle, groundwater and interface of stratum, etc. The ground model includes engineering parameters that are based on the geologic model, such as cohesion and friction angle. The geotechnical model is a tool for predicting and analyzing by adding design parameters to the ground model, such as the limit equilibrium method and numerical analysis models. This study takes the uncertainty of the geological model as the main discussion aspect and takes the sources of different dip angles and their critical groundwater pressure as the basis for the uncertainty. It is assumed that there are three types of failure modes: rail pile erosion, stability rail pile and in front of the rail pile with tension crack. The failure modes and the analysis scenarios of four combinations of dip angles and groundwater pressure uncertainties are analyzed using the limit equilibrium method and Monte Carlo simulation. Finally, the influence of failure probability on slope stability is discussed. The analysis result is that the failure probability in the dry state is inversely proportional to the precision of the standard deviation of the dip angles. The influence of different failure modes on the failure probability is that the failure probability of the mode in front of the rail pile with tension crack is the largest, which is consistent with the situation observed in the field investigation. The results under the condition of considering the critical groundwater pressure, if do not consider the difference in dip angle precision, the overall analysis results show that the sensitivity of dip angle variability to failure probability is higher than groundwater pressure variability. In this study, a three-dimensional numerical model is also used to explore the failure conditions of the study area under extreme conditions of changing the different combinations of discontinuity cohesion and friction angle. The results show that the overall study area is fairly stable under non-extreme conditions.
