Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/55727
標題: 氣候與地震劇變對堰塞湖演變機制及災害防治之研究-子計畫:堰塞湖潰堤之破壞機制分析
Failure Mechanism of Landslide Dams
作者: 馮正一
關鍵字: 其他(理), 水土資源保育;應用研究;landslide dam;堰塞壩;破壞機制;滲流;沖蝕;地球物理探勘;數值模擬;failure mechanism;seepage;erosion;geophysical exploration;numerical simulation
摘要: 
堰塞壩主要為地震、暴雨等自然外力引發河岸邊坡崩塌,致使大量土石滑落堵塞河道所形成之天然壩體。其材料粒徑分布極為不均且結構鬆散,穩定性遠不如人造土石壩,堰塞壩極可能不預期地潰決,演變成嚴重之二次災害。因此本計畫「堰塞湖潰堤之破壞機制分析」將透過滲流模擬、靜力穩定性分析、地震動態反應分析及壩頂溢流沖蝕耦合模式研擬,進入瞭解堰塞壩破壞機制,作為未來預測堰塞壩潰決、降低堰塞湖潛在災害相關處理之參考。為瞭解堰塞壩材料特性及組成,本研究以地電阻剖面法(ERT)與表面波譜法(SASW)兩種非破壞性地球物理探測法,進行堰塞壩體地下水及材料參數之調查。地電阻剖面法可藉由堰塞壩電阻率量測,推估壩體內部地層與地下水位大致分布情形;表面波譜法則量測雷利波到達時間取得頻散曲線以計算地層波速與深度變化之關係,可反算得到土層之剪力模數剖面。透過地電阻剖面法及表面波譜法,可快速、經濟、有效地分析堰塞壩之材料性質,並初步探討壩體材料組成與潰壩之關聯性。為探討水位溢頂前降雨及地震對於堰塞壩應力狀態變化之影響,本計畫採用快速拉格朗日有限差分法FLAC 程式,進行從靜力狀態滲流至動力狀態之一貫化分析,並以離散元素數值分析軟體UDEC 程式,模擬堰塞壩體中不均勻岩塊裂縫之滲流與力學行為。整合兩種數值方法之分析結果,可評估堰塞壩在未溢頂的情況下,受外力影響之靜態及動態穩定特性。堰塞壩體顆粒材料受溢流沖蝕為堰塞壩最常見之破壞形式, 本研究發展FLAC-PFC2D 耦合數值模式分析其沖蝕行為,將探討含連續體與顆粒流的雙重複雜破壞機制,並進行堰塞壩溢流沖蝕時壩體變形、應力分佈及壩體表面顆粒材料崩落過程之模擬。

Landslide dams are formed by large amount of slope failure materials filled in rivers dueto strong earthquake and rainfall. The materials are very inhomogeneous and in a veryloosen state. Therefore, the stability of a landslide dam is not as good as a man-made earthdam. Landslide dams could be breached unexpectedly causing severe secondary hazards todownstream.This project, "Failure Mechanism of Landslide Dams", proposes using seepagesimulation, static stability analysis, earthquake dynamic analysis, and coupling analysis foroverflow erosion to better understand the failure mechanism of landslide dams. The resultscan be a reference got predicting dam breaching and reduce its potential hazards.To understand the material properties of the landslide dams, this study adoptsgeophysical exploration method including Electrical Resistivity Tomography (ERT) andSpectral Analysis of Surface Waves (SASW) to investigate groundwater condition andmaterial parameters. Using ERT method to measure resistivity of landslide dams, thegeneral water level and dam material distribution can be obtained. Using SASW method tomeasure the arrival time of Rayleigh waves, the dispersion curves can be obtained tocalculate the wave velocity (shear modulus) versus depth of the dam materials. Using ERTand SASW method, the properties of landslide dam materials can be quickly and effectivelyestimated for discussing the relationship between dam breaching and dam constitutingmaterials.To investigate the influence of rainfall and earthquake on stress variation of dammaterials, the Fast Lagrangian Analysis of Continua code, FLAC, is applied tosystematically analyze the static, seepage and dynamic condition of the landslide dam. Thedistinct element code, UDEC, is used to analysis the seepage and mechanical behavior of thecracks in landslide dam materials. By integrating the results from the two analyses, thestability of landslide dams under static, dynamic and seepage conditions can be detailedevaluated.The surface particles on landslide dam eroded by overflow is a common failuremechanism. This study develops a coupling numerical simulation scheme using particle flowcode, PFC2D, and FLAC to analyze erosion behavior. The complex failure mechanismdiscussed will include stress and deformation interactions between particle flow materialsand continuum materials. The progress failure of surface particles on landslide dam duringoverflow erosion will be simulated.
URI: http://hdl.handle.net/11455/55727
其他識別: NSC99-2625-M005-004-MY3
Appears in Collections:水土保持學系

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