動態離心模型試驗探討含薄沉泥夾層的砂層之液化機制; Liquefaction mechanism in layered sand using dynamic centrifuge modeling test

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Title:	動態離心模型試驗探討含薄沉泥夾層的砂層之液化機制;Liquefaction mechanism in layered sand using dynamic centrifuge modeling test
Authors:	連紘震;Hung-Chen Lien
Contributors:	土木工程研究所
Keywords:	離心模型振動台試驗;薄沉泥夾層;砂層液化;geotechnical centrifuge shaking table tests;liquefaction of sand;thin silt intra-layer
Date:	2010-06-28
Issue Date:	2010-12-08 13:32:52 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究利用1-D離心模型振動台試驗，探討含薄沉泥夾層的疏鬆砂層之液化機制。藉由二組在不同深度含薄沉泥夾層的砂試體以及一組純砂試體，三組砂試體的相對密度相同、利用相同黏滯係數的孔隙流體來飽和試體，並且以相同的振動振幅施以水平振動，觀察薄沉泥夾層對震波傳遞、液化的深度及範圍、液化延時、孔隙水壓分布和消散及地表沉陷的影響，藉此探討薄沉泥夾層對砂土液化所扮演的角色及其工程上的影響。研究結果顯示：(1)含薄沉泥夾層的砂土層，液化發生的範圍與沉陷量較小。(2)薄沉泥夾層出現在近地表處時，只在沉泥層下方液化。若薄沉泥層出現於深層時，不單沉泥層下方砂土發生液化，連上方也會液化。(3)當液化發生時，剪力波無法直接傳入上部液化砂層，因此能量會因反射集中在液化層下方，因此位於深層的薄沉泥夾層相較淺層的薄沉泥夾層，底部的超額孔隙水壓之激發會較大。 Three dynamic centrifuge modeling tests were conducted to simulate the seismic response for the sandy soil deposits without a silt intra-layer and with a thin silt intra-layer at various depths. These three models had the same relative density and were saturated with the same viscosity pore fluid and were finally subjected to the same magnitude of base acceleration. The aim of this study is to investigate the effect of low-permeability thin silt intra-layer at the different depths in a loose sand deposit on the generation and dissipation of excess pore water pressure in the sand deposit, the shear wave propagation, the surface settlements and the related liquefaction mechanism. The test results show that (1) the thin silt intra-layer in the sand deposit can reduce the extent of liquefaction and the surface settlement; (2) liquefaction occurs only in the sand beneath the thin silt layers near the surface. However, for the deeper thin silt intra-layer, liquefaction occurs not only in the sand beneath the thin silt layers but also in the sand near the surface; (3) the shear wave cannot propagate to the top of liquefaction layer, and the wave will reflect back, therefore, the sand deposit with the deeper thin silt intra-layer has greater excess pore water pressure due to deeper liquefaction.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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