英文篇名
Material Point Method Analysis of Post-Failure Process and Kinematic Behavior of Landslides: Use Maokong Slopes as Examples
作者
楊國鑫、吳昱葵、鄧福宸、陳昭維、陳仁達
關鍵字
物質點法、山崩、大變形分析、崩塌過程、山崩運動行為
摘要
山崩後土壤運移與堆積的範圍,以及是否會影響到下邊坡的保全住戶,為防災與工程實務中所關切重要議題。本研究選用物質點法(material point method)分析探討邊坡破壞後之崩塌過程與運動行為、如山崩速度、土壤運移距離、堆積高度等。本文針對台北市貓空兩處邊坡歷史災害進行研究,兩處邊坡皆因2008年9月薔蜜颱風造成崩塌,崩塌範圍皆涉及至重要保全對象。文中首先將數值模擬結果與兩處邊坡崩塌後的實測地形剖面進行驗證比對,隨後透過數值分析結果,觀察邊坡破壞後之軸差應變、體積應變、以及孔隙水壓,以了解邊坡崩塌的運動過程與力學機制。研究結果發現物質點法能夠準確預測兩處邊坡的運移距離,然而若因土壤堆積受現地三維扇形擴散效應的影響,以二維數值模式會稍微高估山崩後土壤的堆積高度。此外,與不排水模式比較,水力耦合模式因能模擬邊坡崩塌過程的中土壤孔隙水壓的激發與消散,故能較準確預測土壤的運移距離。
英文摘要
The runout distance and deposit height of landslides are important issues for landslide disaster mitigation and prevention. This paper presents a series of numerical analyses using the material point method (MPM) to investigate the post-failure and kinematic behavior of landslides (i.e., landslide velocity, runout distance, deposit height). Two landslide cases in Maokong, Taipei, are studied. The slope failures were triggered by Typhoon Jangmi in September 2008 and has a significant impact on the residence downslope. The numerical models are first validated by comparing the predicted results with the measured slope profiles after landslides. After the validation is confirmed, the numerical results (i.e., deviatoric strain, volumetric strain, and porewater pressure) are further examined to understand the failure process and mechanism of the landslides. The numerical results reveal that the MPM can accurately predict the runout distance of both landslide cases, but overestimate the deposit height due to the limitation of the two-dimensional analysis. Besides, compared to the undrained analysis, the fully coupled analysis allows the dissipation of pore water pressure during the landslide, resulting in a better prediction on the landslide runout distance.