牽引式深層崩塌之發生機制探討－以四川漢源萬工滑坡為例

2010年7月23－25日於中國四川省漢源縣萬工鄉二蠻山降下豪雨（最大降雨強度50mm/hr），25日溪溝土石流持續出現約6小時。7月27日04:00引發了大型高速滑坡災害（崩塌區料源約48×10^4m^3），滑坡體長達1.6km，堆積土方量約120×10^4m^3。造成下游新市鎮移民區92戶房屋毀壞，21人失蹤，1500人被迫疏散遷移。該災害主要成因為臨前降雨，引起溪溝內之土石流流動，促使原坡面堆積物之坡腳淘蝕失穩，進而啟動料源區玄武岩坡面風化層之崩解與滑坡碎屑流，滑坡土體高速撞擊停止後，在溪床內繼續形成二次緩慢流動，直至下游集鎮處。現地調查分析說明該災害主要與土體受降雨飽和、特殊地貌特徵、地下水位入滲及地層交界帶（石灰－玄武岩）之弱面構造有關，為一高強度降雨下，土石流牽引大規模深層滑坡之特殊共生案例。

關鍵字

土石流；牽引式滑坡；降雨；沖刷作用

並列摘要

The heavy rainfall (50mm/hr) of July 25, 2010 produced a large-scale of rapid, retrogressive landslide in Ermanshan mountain, Hanyuan county, Sichuan, China at the daybreak of July 27. The landslide was characterized by ~1.6 km runout distance and a sliding mass with a volume of 120×104 m3. It caused a total of 1500 residents were evacuated and damaged 92 houses. Later official report indicated that 21 resident died in the geological disaster. The cause of the catastrophe originated in the debris flow occurred on 7/25 induced by former intense precipitation. The fluidization behavior of debris flow scoured the toe of slope and triggered the intensely weathered basalt at the source area to collapse into the steep gulley. The deposition mass continued to develop a second flow (creep motion) and push over the downstream buildings after the first rapid collision of both fragmental rock and sliding mass ceased. The field survey showed the dominant factors causing initial landslide are associated to the saturated soil mass from the rainfall, special terrain features with a high drop height, ground water seepage, and the presence of weak-surface between basalt and limestone stratum. The case could be concluded a typical event of deep landslide induced by the former debris flow.

並列關鍵字

Debris Flows ； Retrogressive Landslide ； Rainfall ； Scouring

國際替代計量

牽引式深層崩塌之發生機制探討－以四川漢源萬工滑坡為例

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