規則波形之砂地盤受震反應:離心試驗與數值模擬

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题名:	規則波形之砂地盤受震反應:離心試驗與數值模擬
作者:	陳奕心;Chen, Yi-Sin
贡献者:	土木工程學系
关键词:	土壤液化;地盤反應分析;動態強度試驗;DEEPSOIL;離心模型試驗;soil liquefaction;ground response analysis;DEEPSOIL;centrifuge test
日期:	2022-08-08
上传时间:	2022-10-04 10:46:31 (UTC+8)
出版者:	國立中央大學
摘要:	台灣位於菲律賓海板塊與歐亞大陸板塊的交界帶，因此時常發生地震，而地震期間可能會伴隨著土壤液化的發生，導致地表沉陷、建築物倒塌等災害。故本研究以離心機模型試驗之數據，分析自由場砂土層在不同深度的受震反應，並利用一維地盤反應分析軟體DEEPSOIL搭配動態強度試驗之結果擬合土壤模型及孔隙水壓生成模型進行模擬與分析，最後探討離心模型試驗與數值模擬分析之地盤的受震反應。研究結果顯示，當土層尚未液化時，越接近地表的土層，加速度振幅及尖峰地表加速度會越有放大的趨勢，傅氏譜幅值具有放大效應，且在頻率為1Hz及3Hz處可觀察到較明顯的峰值;而當土層發生液化時，剪力波便無法順利傳遞，導致加速度振幅及尖峰地表加速度會有衰減的趨勢，頻率為1Hz及3Hz處之傅氏譜幅值會有縮小的現象，反而在較高頻處有放大的現象。且隨著震動強度的增加，識別出之土層主頻會隨之減小。以DEEPSOIL透過給定恆定阻尼比模擬乾砂試體，使數值模擬結果為最符合離心模型試驗結果，再將其動態性質與共振柱試驗結果比較，可以發現在相同剪應變下，DEEPSOIL所設定之阻尼比與共振柱試驗獲得之阻尼比皆不會相差太多。以DEEPSOIL透過調整孔隙水壓模型參數模擬飽和砂試體，使數值模擬與離心模型試驗結果為最相符的狀態，可觀察到調整參數後數值模擬的加速度振幅皆與離心模型試驗的振幅更相符。數值模擬於淺層處激發的超額孔隙水壓皆高於離心模型試驗的結果，而數值模擬於緊砂層所激發的超額孔隙水壓皆低於離心模型試驗的結果。 ;Taiwan is located at the junction of the Philippine Sea Plate and the Eurasian Plate, so earthquakes often occur. During the earthquake, soil liquefaction may occur, resulting in surface subsidence and building collapse. Therefore, this study uses the data of the centrifuge model test to analyze the seismic response of the free-field at different depths and uses the one-dimensional ground response analysis software DEEPSOIL to match the results of the dynamic test to fit the soil model and the pore water pressure generation model. Finally, the centrifuge model test and numerical simulation analysis of the seismic ground response are discussed. The results show that when the soil layer has not liquefied, the closer the soil layer is to the surface, the more the acceleration amplitude and the peak ground acceleration will be amplified. When the soil layer is liquefied, the shear wave cannot be transmitted, resulting in the tendency of acceleration amplitude and peak ground acceleration to decrease. And as the vibration intensity increases, the predominant frequency of the identified soil layer will decrease accordingly. Using DEEPSOIL to simulate the dry sand sample through a given constant damping ratio, the numerical simulation results are most consistent with the results of the centrifuge model test. The damping ratio is not much different from the damping obtained from the resonant column test. Using DEEPSOIL to simulate saturated sand by adjusting the pore water pressure model parameters, the results of the numerical simulation and the centrifuge model test are most consistent. The excess pore water pressure excited by the numerical simulation in the shallow layer is higher than that of the centrifuge model test, while the excess pore water pressure excited by the numerical simulation in the tight sand layer is lower than the result of the centrifuge model test.
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