本研究利用三種不同樁徑比(L/D=8.4, 14.3, 19)之模型基樁，其基樁長度皆相等，在1g狀態下進行貫樁，其貫入深度為19cm。接著使離心機繞到80g時，進行基樁受反覆循環荷載試驗，探討現地原型尺寸基樁受相同壓、拉循環載重下樁土間反應行為。 本試驗施加荷載方式分為兩種:(1)先施加壓力，解壓後再施以拉拔力(2)先施加拉拔力，解除拉拔後，再施以壓力。過程中利用複動式氣壓缸控制荷載，進行五次循環荷載之加載卸載。試驗所得初步結果顯示，離心加速度增加過程中土壤沉陷量大於樁頭沉陷量，此時樁身產生負摩擦力影響，樁身β值隨著長徑比變小而增加。將達到目標g數80g所量測到之軸力數據歸零後，再進行後續循環荷載試驗。結果顯示樁身勁度會隨著循環次數越多而增加，阻尼比則隨著循環次數增加而減少。在基樁解除拉拔力後樁底周圍土壤會對基樁產生一束制力影響，使基樁底部承受拉力，爾後增加壓荷載時樁底拉力則隨之減少。 A series of centrifuge modeling tests was conducted in the study to investigate the behavior of piles subjected to two types of cyclic axial loadings, including the compressive-tensile and tensile-compressive modes. Three kinds of piles were selected with different slender ratios but with the same embedded length. The model pile was slowly penetrated into the dry sand at 1g condition. Then, the tested model was set on the platform of centrifuge and subjected to an artificial gravity of 80g to simulate a full-scale prototype pile. Subsequently, five cycles of axial cyclic loadings were applied on pile head by a double active air cylinder. From the test results, it can be found that the stiffness of pile increases with increasing number of cyclic loading. The damping ratio increases with decreasing slender ratio. Besides, a tensile force occurs near the bottom of the pile resulting from the release of the tensile force at the pile head.
