利用數值模試模擬地震引致的邊坡滑動行為

Abstract

摘要 台灣位於歐亞板塊及菲律賓板塊交界處，板塊互相擠壓造成地盤抬升速度較快，使得台灣地區山多且陡，又因氣候多雨且板塊運動造成地震頻繁，使得邊坡滑動的情形層出不窮，加上台灣地區人口密度高，在土地資源不足的情況下於是往山區發展，因此邊坡滑動往往造成人員及財產上的損失。有鑑於此，若能模擬出邊坡滑動的影響範圍，則可事前預知及防止災害發生。 本研究利用數值方法，包括Newmark 法及有限元素法的數值軟體來模擬由地震力引致的邊坡滑動情形，希望能夠建立一套適合應用於邊坡滑動的數值模擬模式，以計算邊坡滑動的臨界加速度、滑動時間點以及滑動距離。本研究是以連續體及塊體滑動建立邊坡滑動模式，首先對於林美聆及王國隆(2009)於國家地震中心所進行的「大型模型邊坡之振動台試驗」作數值模擬，利用已知的材料參數以及振動頻率與振幅建立滑動模型，其塑性區分佈視為破壞面可能發生的位置。最後將模擬滑動的結果與試驗結果比對，且進行參數敏感度分析，校正參數之適用性及找出影響邊坡滑動量的因素。模擬完大型模型邊坡振動台試驗後，進而將此模式應用於現地南投縣鹿谷鄉和雅滑動邊坡，由於和雅滑動邊坡於921 大地震後邊坡上方出現一寬約2 公尺的裂縫，加上此地區為順向坡地形，且砂頁岩互層交界處有明顯的弱面存在，因此未來有發生邊坡滑動的風險，本研究將利用數值模型模擬在921 地震下裂縫的產生，以及若此地區滑動塊體發生滑動的情形下，其滑動距離的大小。 本研究結果顯示，利用數值方法可成功模擬出大型模型邊坡之振動台試驗，其滑動距離及滑動時間點皆符合試驗結果；現地邊坡之模擬也可推測滑動面的位置及滑動距離，因此可以利用此數值模式來模擬邊坡滑動的運動情形。

Taiwan lies in the interjunction of Eurasia and Philippines sea plates, the platescollide with each other causing the rugged landscape. However, massive rainfall andearthquake often trigger landslides, which may lead to serious casualties and loss of properties. If the run-out of landslides could be simulated, then we can take some precautions against the hazard, so its applications are quite extensive. This study is based on the continuous mechanics and sliding-block analysis, two numerical methods in this study, Newmark method and FEM, numerical models were established to simulate the earthquake-induced landslides behavior, including run-out distance, critical acceleration, and initiation time. The data of large scale-shaking table test by Wang and Lin (2009) were used for simulation and results were compared with the results of experiment. The plastic zone is considered the location of failure plane,and parameter studies were also performed to find out the effects of each factor on the run-out distance. The numerical model was applied to the field case at Hoya village in Nantou County, the 921 earthquake acceleration record was applied to the bottom of the model,and estimated sliding surface to simulate the crack development and the run-out distance. The result shows that the continuous mechanics numerical model can simulate well with both cases, and the run-out distance and starting time fit the experiment results; Therefore, numerical model can simulate the earthquake-induced landslides well.