邊坡穩定性問題一直是土木工程與地質工程領域的重要課題，尤其是在多雨地區，其對基礎設施安全與人類生命財產具有直接影響。本研究以關子嶺邊坡為案例，分析降雨入滲如何增加孔隙水壓、降低有效應力，最終引發邊坡失穩。傳統的邊坡穩定性分析方法主要依賴極限平衡法（Limit Equilibrium Method, LEM）和有限元素法（Finite Element Method, FEM）等數值方法。儘管 LEM 計算效率高，且在工程實務中廣泛應用，但其僅能提供整體穩定性指數，無法詳細呈現內部應力或變形；而 FEM 能捕捉邊坡內的應力–應變關係，但其基於網格的計算方法在大變形情境中易產生嚴重的網格變形。
為了克服上述方法的局限性，本研究採用物質點法（Material Point Method, MPM）進行模擬，能夠準確模擬大變形與流體–固體耦合現象。在進行關子嶺邊坡分析前，本研究首先通過 MPM 的模擬結果與先前的物理試驗數據及其他數值方法進行驗證，比對結果顯示模型具有高度一致性與合理性，為後續分析奠定了理論基礎。隨後，以關子嶺潛在崩塌邊坡為例，先透過 MPM 分析估算破壞深度，作為滑動體幾何的建構基礎，再結合理想化崩塌曲面（Idealized Curved Surface, ICS）建立滑動初始形狀，進一步導入雙相流模型 MoSES_2PDF 模擬滑動與堆積行為，呈現崩塌過程從觸發至傳輸的完整發展。藉由 MPM、ICS 與 MoSES_2PDF 的整合，實現具三維地形對應能力的崩塌模擬流程，並應用於關子嶺實際地形，成功解析滑動行為與堆積區域空間分布，為後續災害潛勢評估與防災設計提供具體參考。

Slope stability has long been a critical issue in the fields of civil and geotechnical engineering, particularly in regions with heavy rainfall, where it directly impacts infrastructure safety and human life and property. This study investigates the Guanziling slope as a case study to analyze how rainfall infiltration increases pore water pressure, reduces effective stress, and ultimately triggers slope failure. Traditional slope stability analysis methods primarily rely on the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM). While LEM offers high computational efficiency and is widely used in engineering practice, it can only provide an overall safety factor without capturing internal stress or deformation. FEM, on the other hand, can simulate the stress–strain behavior within the slope but often suffers from severe mesh distortion under large deformation conditions due to its grid-based nature.
To overcome these limitations, this study adopts the Material Point Method (MPM), which is capable of accurately modeling large deformations and fluid–solid coupling behavior. Prior to the Guanziling slope analysis, the MPM model was validated against physical experiments and other numerical methods. The comparison shows high consistency and reliability, thereby establishing a solid theoretical foundation for the subsequent analyses. Using the estimated failure depth from MPM as the geometric basis, an Idealized Curved Surface (ICS) was then constructed to define the initial shape of the sliding mass. This geometry was further input into the two-phase flow model MoSES_2PDF to simulate the full landslide process from failure initiation to subsequent runout and deposition. By integrating MPM, ICS, and MoSES_2PDF, this study develops a three-dimensionally consistent landslide simulation framework and applies it to real terrain data of Guanziling, successfully identifying sliding behavior and depositional zones. The proposed workflow provides concrete references for future hazard assessment and disaster mitigation planning.

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