由於土壤之剪力強度對減少樁體承受側向荷重後之側向位移影響很大，且位於黏性土壤淺層處之土壤側向抵抗能力較差，故本研究利用室內土槽進行一系列之側向樁載重試驗，嘗試以增加樁基周圍土壤之側向阻抗力的方法，以瞭解軟弱黏土中基樁承受側向荷重後之力學行為，減少其樁頭側向位移與增加側向荷載能力。 在黏土未改良前與經改良後兩種情況下，進行模型樁側向荷重試驗，比較改良前後側向荷重和樁頭位移與樁身彎矩之差異，並討論模型樁位移、彎矩與改良範圍和改良配比之間的關係。 由試驗結果得知，在實驗之最大荷重作用下，其結果顯示以邊長6~8倍樁徑的正方形改良面積，與4~6倍樁徑以內的改良深度之方體改良範圍，回填經水泥配比1%改良後之改良拌和土，對於減少模型樁側向位移有最經濟的效果。 當固定改良面積和改良深度時，改良配比在5%~10%內即可得到良好的改良效果，超過10%後改良效果隨改良配比增加而增加的趨勢則不顯著。對接近地表之土層中進行局部之土壤改良，且在黏土中添加少量之改良材料，便可有效減少樁體之側向位移。 The behavior of piles under lateral loading is important to the safety of construction. The magnitude of the lateral displacement of the pile under lateral loading depends on the shear strength of soil, and the lateral resistance of soil toward the ground surface is weak because of the lack of confining pressure. This research carried out a series of model pile tests to understand the mechanical behaviors of single pile under lateral loading in soft clay, and to analyze which scope of treated soil around the pile foundation can increase the lateral resistance and reduce the horizontal displacement. The research compares the lateral properties of model piles in treated and untreated clays. The experimental results of the model pile tests in soft clay indicate that the treated area with the dimension of 6D~8D in width of square and 4D~6D in depth (where D is the diameter of pile) can achieve economical improvement effects in reducing the horizontal displacement of model piles. Under the condition of constant shape and volume with a cement content lower than 10％, it showed noticeable improvement effects in reducing the horizontal displacement of model piles. By using a small quantity of cement material to treat the soil in the vicinity of pile head can decrease the lateral displacement of the pile significantly.
