本研究以「台20線52 K+000卡努颱風災害路基保護修復工程」為研究案例，針對具長期滑動潛勢之公路邊坡，建立一套以整體邊坡反算模型為核心，並切分上、下邊坡以局部邊坡之面向，探討不同補強配置與地下水位條件下之邊坡穩定行為。研究目的不僅在於比較安全係數之變化，更著重於臨界滑動面之辨識及其於整體邊坡穩定性評估中的關鍵角色。研究結果顯示，於高地下水位且未施作補強之情況下，整體邊坡變形主要以下邊坡先行破壞為特徵，較深層滑動行為易受整體位移與表層滑動所掩蓋。透過整體模型結合子模型分析，可有效辨識影響整體邊坡穩定性之臨界滑動面。進一步分析顯示，表層補強措施主要可抑制坡面變形並使臨界滑動面得以顯現，對整體穩定性之直接提升有限。本研究結果證實，當整體邊坡模型建立完成且臨界滑動面得以明確辨識後，即可於同一分析架構下，預先評估不同補強配置或設計方案對施工後滑動行為與整體穩定性之影響，使邊坡穩定分析由單次結果驗證提升為具備預測能力之工程工具，對邊坡補強設計與工程審核作業均具高度實務應用價值。

This study takes the Rehabilitation Project for Roadbed Protection at Highway No. 20, 52K+000, Damaged by Typhoon Khanun as a case study to investigate the stability behavior of a highway slope with long-term sliding potential. A numerical analysis framework is established with a back-analyzed global slope model as its core, complemented by upper- and lower-slope sub-models, to examine slope stability under different reinforcement configurations and groundwater level conditions.Rather than focusing solely on variations in the factor of safety, this research emphasizes the identification of critical slip surfaces and their governing role in evaluating overall slope stability. The results indicate that under high groundwater conditions without reinforcement, slope deformation is characterized by initial failure in the lower slope, while deeper sliding behavior tends to be obscured by overall displacement and shallow surface movements. By integrating global and sub-model analyses, the proposed framework effectively identifies the critical slip surface that controls overall slope stability.
Further analyses reveal that surface reinforcement measures primarily suppress shallow slope deformation and facilitate the manifestation of the critical slip surface, but contribute limited direct improvement to overall stability. The findings demonstrate that once a reliable global slope model is established and the critical slip surface is clearly identified, the same analytical framework can be used to proactively evaluate the effects of various reinforcement configurations or design alternatives on post-construction sliding behavior and overall stability. This approach advances slope stability analysis from a single-case verification method to a predictive engineering tool, offering significant practical value for slope reinforcement design and engineering review processes.

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