本研究的試驗土樣取自於湖山水庫借土區殼層SM與ML土壤。利用特製夯模製作標準夯實能量下之重模試體，並以改良飽和方法使夯實試體達飽和。由於土石壩是採用分區滾壓夯實構築而成，壩體內部的靜態應力除了水平與垂直應力外，尚包含初始剪應力，故需考慮非等向壓密狀態，本研究控制有效圍壓於0.5及2.0kg/cm2，施作等向壓密Kc( )=1.0與非等向壓密應力比Kc=1.5和Kc=2.0狀態下三種夯實土壤之動力三軸試驗，探討夯實土壤於不同有效圍壓及壓密應力比的動態強度、孔隙水壓及變形之特性。 試驗結果顯示夯實土壤不會發生初始液化之現象，在等向壓密與非等向壓密下，相近反覆應力下所激發之極限殘餘孔隙水壓隨有效圍壓增加而降低；壓密應力比越大受反覆荷載作用下所激發之超額孔隙水壓量小，而極限孔隙水壓比隨著壓密應力比增加而下降。由應力路徑可觀察夯實土壤反覆受剪後，有顯著的剪脹性，動態變形量也會隨作用週數趨於穩定，故可推測夯實土壤於震後僅會發生有限的變形。殼層SM土壤在壓密應力比Kc=1.0及1.5時，動態剪應力比隨著圍壓增加並未有降低現象，而在Kc=2.0即可看出動態剪應力比隨圍壓增加而降低；殼層ML土壤其動態剪應力比隨圍壓增加而降低。並將試驗結果整理成不同有效圍壓及壓密應力比下反覆剪應力與剪應變之關係及再壓密體積應變與剪應變關係曲線，可用於估算土石壩受震所產生之永久變形與沉陷，供工程界參考。 The study is to investigate dynamic strength of saturated compacted soils. Dynamic strength of saturated compacted soils is very important parameters in analyzing seismic responses of earth dam materials. This paper performed a series of stress-controlled dynamic triaxial tests on two kinds of compacted soils, SM and ML for constructing an earth dam. This paper proposed a vacuum method for improving the saturation of compacted soils. Test results indicate the methods make the Skempton’s coefficient B of all specimens greater than 0.95. Compacted soils of the earth dam have different initial shear stress conditions which range from Kc=1.5 to Kc=2.0. The ultimate pore water pressure decreased when the effective confining pressure increased in all kinds of soils. As the effective confining pressure increased, the cyclic shear stress ratio of compacted SM soils is almost constant for anisotropically consolidated Kc=1.0 and 1.5 conditions. However, the cyclic shear stress ratio decreased in the conditions of compacted SM soils in anisotropically consolidated Kc=2.0 and compacted ML soils. In order to evaluate the post earthquake settlement, the drained values are opened after cyclic loading completed and excess pore water pressure dissipate with time induce volumetric strain. The consolidated stress ratio increased, the post volumetric strain decreased.
