飽和度對高嶺土之剪力模數及阻尼比影響的實驗研究

Abstract

本研究旨在探討飽和度對高嶺土在共振柱試驗中微小應變條件下的剪力模數、阻尼比的影響。圍壓與孔隙比是影響微小應變下剪力模數的主要因素，圍壓較高且孔隙比較低時，微小應變之剪力模數會較大。然而，當飽和度增加時，粉質土的小應變剪力模數會降低。本研究製作一系列高嶺土非飽和試體進行共振柱試驗，聚焦於固定孔隙比與圍壓條件下，飽和度對高嶺土剪力模數是否產生類似影響，並將高嶺土之夯實曲線為基礎，觀察乾側與濕側是否有相同性質，同時觀察試體體積變化量，獨立計算出空氣體積及其施加圍壓過程中壓縮程度，求出實際試體孔隙比；此外，本研究除了改變不同變因進行共振柱試驗並提出相關模型回歸出預測的微小應變下最大剪力模數。從結果得知，在微小應變下進行共振柱試驗，乾側與粉質土之結果相似，孔隙比固定飽和度增加時剪力模數降低的趨勢，圍壓條件上升時也出現較大的剪力模數，以三參數模型回歸發現有很好的結果，而濕側則並未出現相同趨勢，受孔隙比與飽和度限制以及儀器限制在求最大剪力模數時存在誤差，探討圍壓變因的影響並未能有效解釋，因此回歸模型時並未發現明顯趨勢；阻尼比方面則與剪力模數衰減曲線相關，隨剪應變上升，剪力模數衰減曲線越平緩，阻尼比更趨於平緩上升。

This study aimed to investigate the influence of degree of saturation on the shear modulus and damping ratio of kaolinite under very small to medium-strain conditions using resonant column testing. Previous studies have shown that increasing saturation typically leads to a reduction in small-strain shear modulus in silty soils. To examine whether the similar trend applies to highly plastic kaolinite, a series of unsaturated specimens were prepared and tested under resonant column loading. This study focused on evaluating the effect of saturation while holding void ratio and confining pressure roughly constant, and comparing the specimen behavior prepared based on the dry- and wet- sides of the compaction curve. Additionally, volumetric changes in the specimens were monitored to understand the deformation behavior of the unsaturated specimens during vibrational loading. The results indicated that under small-strain condition, the behavior of dry-side kaolinite resembled that of silty soils: shear modulus decreased with increasing saturation at fixed void ratio, and increased under higher confining pressure. In contrast, the wet-side specimens did not exhibit the same trend, which was likely due to limited void ratio and saturation ranges. With respect to the damping behavior, the damping ratio curve shifts up as the degree of saturation increases. Additionally, correlation models were developed to predict the maximum shear modulus. The three-variable regression model (saturation, void ratio and confining pressure) provided good predictive performance in this context.