低矮建築物使用微型樁基礎之抗液化效果-離心模型試驗

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題名:	低矮建築物使用微型樁基礎之抗液化效果-離心模型試驗
作者:	張書維;Zhang, Shu-Wei
貢獻者:	土木工程學系
關鍵詞:	微型樁;離心機動態試驗;土壤液化;低矮建築物;small size pile;dynamic centrifuge test;soil liquefaction;low-rise building
日期:	2022-03-23
上傳時間:	2022-07-13 18:05:39 (UTC+8)
出版者:	國立中央大學
摘要:	本研究使用動態離心機模型試驗模擬五層樓建築物在基腳板設置微型樁基礎之抗液化耐震行為。模擬地盤厚20m，淺層5m 為液化土層，以下為較緊密之非液化砂土層 (Dr = 80 or 95%)或混和土層。小口徑樁直徑為33cm，貫入非液化土層深度分別為樁徑之 2、6與10倍，以探討貫入非液化層深度、不同相對密度與非液化層置換為不透水層之影響。五層樓建築物重量與基腳尺寸設計，依照台灣常見之單棟五層樓RC公寓進行設計。在基盤輸入由小到大輸入不同震度之實際地震與正弦波加速度運動歷時，觀察模型於地震期間與震後之受震行為。對照試驗組為無微型樁基礎之淺基腳五層樓建築物模型。在觀測到土層的主頻為2.0 ~ 2.4 Hz且微型樁基礎的主頻為1.0 ~1.2 Hz狀況下試驗結果顯示，總體土層之超額孔隙水壓消散方向為建築物陣列往自由場陣列且深層往表層的方向消散。微型樁基礎具有明顯抑制建築物在震動過程中以及結束後傾角產生的效果，且在設置微型樁基礎、增加微型樁基礎的貫入深度後也具有明顯抑制建築物在震動過程中以及結束後的沉陷產生。且在震動過程中觀測到軸力形式之微型樁基礎在軸力歷時中具有軸力值尖峰反向之行為，彎矩形式之微型樁基礎則在彎矩歷時中具有彎矩值尖峰同向之行為。震動過程中因建築物沉陷量小於周圍地表沉陷量而在微型樁基礎樁身累積負摩擦力，但在震動過程後隨著超額孔隙水壓之消散，微型樁基礎樁身之負摩擦力隨之消散並往正值恢復，並再次提供建築物承載能力。無論是軸力或彎矩形式之微型樁基礎，接隨著淺層土壤液化，往小口徑基樁深度方向增大，顯示因淺層土壤液化喪失承載能力，轉由深層土壤承載。 ;The objective of this research is to use small size pile (micro pile) to reduce settlement and tilt of building in liquefiable soils. Dynamic centrifuge tests were used to simulate the liquefaction mitigation and seismic behavior of a five-story building with footing supported by micro-piles. The model ground is 20m thick, the shallow 5m is liquefied sand layer, and the beneath is dense non-liquefied sand layer or mix layer. The diameter of the micro-piles is 33cm, and the penetration depth into the non-liquefied soil layer is 2, 6 and 10 times of the micro-pile diameter, to explore the influence of the different relative density of non-liquefied sand layer, mix layer and penetration depth. The weigth and footing dimension of the five-story building are designed in accordance with the common sigle five-story RC department in Taiwan. The results show that the domain frequency of the ground is 2.0 ~ 2.4Hz and the domain frequency of building with micro-pile structure is 1.0 ~ 1.2Hz. The tests results show that the dissipation of excess pore water pressure in the soil layer is from building to free field and from deep to surface of the soil layer. The test results show that the micro-piles and increase the penetration depth has the obvious effect of restraining the settlement and the inclination of the building after the earthquake. During the vibration, it was observed that the axial-force instrumented piles had symmetrical reverse axial force waveform, and the lateral instrumented piles had similar and in phase bending moment wave forms. Because the settlement of the building less than settlement of the soil layer, the negative friction force were accumulated on the micro-pile. But after vibration, with the dissipation of the excess pore water pressure, the negative friction on the micro-pile will recover and re-provide bearing capacity of the building. When the shallow soil liquefies, axial force and moment increases in the deeper part of the micro-piles, the shallow soil loses liquefaction and the load is transferred to the deep soil. Key word: small size pile, dynamic centrifuge test, soil liquefaction, low-rese building
顯示於類別:	[土木工程研究所] 博碩士論文

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