以動態離心模型試驗模擬煤灰地盤之受震反應

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题名:	以動態離心模型試驗模擬煤灰地盤之受震反應
作者:	曾維宏;Tseng,Wei-hung
贡献者:	土木工程學系
关键词:	煤灰地盤;土壤液化;砂樁改良;超額孔隙水壓;地工離心機;ash ground;soil liquefaction;excess pore water pressure;centrifuge test
日期:	2014-07-10
上传时间:	2014-10-15 14:22:46 (UTC+8)
出版者:	國立中央大學
摘要:	本研究由林口火力發電場之灰塘採集了重模試體所須土樣，以大型壓密儀進行飽和煤灰試體之製作，並設計了不同煤灰地盤厚度(9m、14m)及砂樁改良模型，利用中央大學地工離心機繞行至50g後進行受振試驗，並在試體內部按不同深度分別埋置加速度計、孔隙水壓計以及架設垂直向之線性差動變壓器，以觀察煤灰地盤受振後液化之動態反應。經研究結果顯示：(1) 土壤未達到液化狀態時，其加速度振幅會隨土層深度越淺而有所放大，且小振動具有較高的放大倍率。土壤液化後由於剪力波無法向上傳遞，因為液化土層中的加速度振幅會呈衰減的趨勢；(2) 經由加速度歷時的對照，液化振動事件時未改良煤灰層之加速度振幅從第一個週期後開始衰減。砂樁改良組的煤灰層保留了前二個週期的完整波型，顯示出經改良煤灰土層之抗液化能力略高於未改良煤灰土層；(3) 綜合加速度與超額孔隙水壓比歷時，未改良煤灰層之液化深度達到8.5m，且超額孔隙水壓激發後所需的消散時間極長。而經過砂樁改良的煤灰層之液化深度同樣達到8.5m，但振動結束後水壓便開始迅速消散，顯示設置砂樁有利於煤灰層的排水。 ;In this research, series of dynamic centrifuge tests were performed to investigate the seismic behavior of liquefiable ash ground with different configuration. The ash samples were collected from the ash pond of thermal power plant in Linkou and made into consolidation samples. Tested models are divided into two groups according to the thickness of ash ground. All the models were installed the accelerometers, pore water pressure transducers and linear variable differential transformers (LVDT) to observe the seismic response of ash ground during and after soil liquefaction. The test results showed: (1) the acceleration amplified from the base of soil stratum to the top while soil was non-liquefaction. On the other hand, the liquefied soil layer obstructs the shear wave propagation causing the decrease of acceleration. (2) The results of acceleration history showed that ash ground with sand pile improvement have slightly higher liquefaction resistance than unimproved ash ground. (3) The dissipation time of excess pore water pressure of liquefaction ash ground is very long. Instead, the excess pore water pressure of ash ground with sand pile improvement dissipated immediately after shaking.
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