| 摘要: | 台灣位處於菲律賓海板塊與歐亞板塊交界帶，在不穩定的板塊邊界導致地震頻繁，地震可能誘發海底山崩進而引起海嘯。海底緩坡崩塌除了破壞海底設施(如海底電纜、海底管線等)，造成經濟損失之外，也可能威脅沿海居民生命安全。西元2006年屏東外海發生海底山崩事件，泥沙崩塌造成海底纜線造成纜線多處斷裂，嚴重影響跨國通訊與電子交易，造成經濟損失。目前人們對海底緩坡受震後之沉積型態了解有限，因此本研究以離心模型試驗以浸水邊坡探討海底緩坡受震之變形行為。
本研究利用中央大學地工離心機進行一系列之動態離心模型試驗，在40 g離心力場中，以浸水邊坡模擬海底緩坡的破壞行為，並且探討輸入不同基盤震動對浸水緩坡受震之變形行為的影響。試驗選用石英砂，以相對密度30 %模擬試體高度10 m且坡度為10°與20°之緩坡土層。五組試驗輸入基盤震動頻率與作用週數皆為1 Hz、15-cycles之正弦波，並透過加速度計、孔隙水壓計、位移計、地表位移計與地中位移計記錄海底緩坡之受震反應。
試驗結果顯示：(1) 10度浸水緩坡之試驗結果得知，累積絕對速度為9.11 m/s的情況下，地表最大位移為2.28 m，受震後試體坡度為2度；(2) 10度浸水緩坡之試驗結果得知，累積絕對速度分別為4.23 m/s與9.11 m/s(增加2.15倍)，地表最大水平位移分別為1.80 m和2.28 m(增加1.27倍)，震後試體坡度分別為6.6度、2.4度；(3)不同坡度(10度、20度)之試驗結果得知，累積絕對速度7.21 m/s與9.11 m/s(增加1.26倍)，震後地表最大水平位移分別2.28 m和2.78 m。
;Taiwan is located at the convergent zones between the Philippine Sea Plate and the Eurasian Plate. Such a complicated convergence has caused frequent earthquakes. The earthquakes probably triggers submarine landslides and then generates near-source tsunamis. Submarine landslides may destroy underwater infrastructure, causing huge economic losses, the tsunami could also be a serious threat to the coastal communities and infrastructures. In 2006, submarine landslide occurred offshore Pingtung; sediments impacted and broke submarine communication cables, affecting international communications and electronic transactions and causing economic losses. At present, the information on the process and deposition of submarine landslides is often limited. This study tries to observe deformation behaviors of submerged gentle slope by centrifuge modeling.
This study conducted five dynamic centrifuge modeling tests to simulate the deformation behaviors of submerged gentle slope by NCU geotechnical centrifuge at 40 g acceleration field. Simulating the failure behavior of submerged slopes with submerged gentle slope. The silica sand is selected for preparing the slope with target relative density of 30%. A submerged gentle slope with 10 m in height is modeled in this study. The slope of the test 10°and 20° A five dynamic centrifuge modeling tests with a frequency content of 1 Hz and 15 cycles sine wave. In this study, accelerometers, pore water pressure transducers, linear variable displacement transformers (LVDTs), surface markers, and spaghetti are arranged to observe the deformation behaviors of submerged gentle slope.
From the test results, it shows that: (1) Under the condition of 10°submerged gentle slope and input base shaking(CAV=9.11 m/s), the maximum surface displacement is about 2.28 m, and the slope after the earthquake is about 2°. (2) Under 10°slope gradient, the cumulative absolute velocity is 4.23 m/s and 9.11 m/s (increased by 2.15 times), the maximum surface displacement is 1.80 m and 2.28 m (increases by 1.26 times), After the earthquake, the slope of the test is 6.6 º and 2.4 º. (3) Under the different slope gradient(10º、20º), when t the cumulative absolute velocity is 7.21 m/s and 9.11 m/s (increased by 1.26 times), the maximum surface displacement is 2.28 m and 2.78 m. |
