土石壩材料之動態性質是土石壩受震反應分析中的重要參數，當土石壩興建完成蓄水後，部分壩體在水面之上，此部分的土石材料為不飽和，而不飽和區之夯實土石材料的動態性質鮮少有文獻探討。本研究之試驗土料來源取自於雲林湖山水庫計畫借土區之兩種殼層材料SM、ML及心層材料CL，試驗針對不飽和夯實土壤，利用共振柱試驗儀求取不飽和試體的動態性質曲線，與飽和試體的動態試驗結果比較探討，並找出最大剪力模數出現最大值時所對應的飽和度，即稱最佳飽和度。 三種土樣的試驗結果顯示，隨著圍壓的增加，動態剪力模數與門檻剪應變皆會增加；隨著試體飽和度的降低，動態剪力模數會增加，而門檻剪應變會隨著飽和度減小而增加。由飽和度與最大剪力模數之關係可看出，夯實SM及ML試體的最佳飽和度出現在4-5 ％ 左右，夯實CL試體在飽和度3-4 ％左右，將試體飽和度與最大剪力模數的關係迴歸出關係方程式，與試體飽和時最大剪力模數的經驗公式結合，整理出各土樣不飽和夯實試體之最大剪力模數的方程式，以供工程界選擇土壤動態性質參數之依據。 Dynamic properties of compacted soils are key parameters in analyzing seismic response of compacted earth dams. The compacted soil of earth dam is composed of saturated part and unsaturated part. However, there’re few literature studying the unsaturated part of compacted soils. This paper aims to analyze the dynamic properties of unsaturated compacted soils. The test materials include compacted SM, ML and CL soils. The dynamic properties of these soils are measured by resonant column test (RCT). The measured properties include the maximum shear modulus, normalized shear modulus, and damping ratio curves in the shear strain range of 〖10〗^(-4)~〖10〗^(-1) % . The results shows that shear modulus and threshold shearing strain are increased with confining pressure. As degree of saturation decreases, shear modulus are significantly increased, but threshold shearing strain is decreased. Therefore, threshold shearing strains of specimens of any saturation degree are almost the same when confining pressure is high. The test results could be combined with current results of saturated specimens. We can get the regressive formula for the maximum shear modulus and use it for future study on seismic response of compacted earth dams.
