以定率法評估邊坡山崩臨界雨量—以南勢坑為例

Deterministic Approach for Estimating the Critical Rainfall Threshold of the Rainfall-induced Nan-Shi-Keng Landslide

10.29417/JCSWC.201303_44(1).0006

鍾明劍(Ming-Chien Chung)；譚志豪(Chih-Hao Tan)；陳勉銘(Mien-Min Chen)；蘇泰維(Tai-Wei Su)

臨界雨量 ； 山崩 ； 定率法 ； 南勢坑 ； Critical rainfall ； landslide ； deterministic approach ； Nan-Shi-Keng

中華水土保持學報

44卷1期（2013 / 03 / 01）

66 - 77

繁體中文

本文採用定率法評估邊坡之山崩臨界雨量。定率法具有明確的物理意義與力學機制，除能評估特定邊坡在不同降雨條件下之崩塌潛勢外，並可藉由邊坡安全係數臨界值觀念反推所對應的臨界雨量。本文所稱山崩臨界雨量定義為暴雨條件下使邊坡安全係數FS達1.0的累積總雨量。山崩臨界雨量研擬程序係先透過現場長期及多場颱風事件之監測資料進行模式回饋分析，以率定及驗證各項水文地質特性參數，建立足以代表現地之水文地質概念模型。再利用此模型輸入不同降雨條件進行關聯性研究以獲得山崩臨界雨量。文中以台南市174線公路50k+650處邊坡為例，透過可考量降雨入滲-滲流-穩定性之串聯式分析模式，獲得其山崩臨界雨量為640 mm。研究成果可供後續防減災措施、保全策略擬訂及坡地預警技術研擬之參考。

In this paper, a deterministic approach is adopted to estimate the critical rainfall threshold of a rainfall-induced landslide. The critical rainfall threshold is defined as the accumulated rainfall when the safety factor of the slope is equal to 1.0. The process of deterministic approach first establishes the hydrogeological conceptual model of the slope based on a series of in-situ investigations and laboratory experimental results. Second, the hydraulic and mechanical parameters of the model are calibrated with the long-term monitoring data. Furthermore, the critical rainfall threshold of the slope can be estimated from the relational analysis between the accumulated rainfall and the slope stability. Finally, the critical rainfall threshold of the slope can be obtained through the integrated analysis of rainfall, infiltration, seepage, and slope stability. Taking the slope located at 50k+650 on Tainan County Road 174 as an example, the results show that the critical rainfall threshold of the study case is around 640 mm. Our preliminary results appear to be useful for rainfall-induced landslide hazard assessments. The findings can also serve as a good reference for establishing an early warning system for landslides.

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