黏土中短樁之側向承載分析一般多以Broms之極限承載理論為主，其分析模式簡單但誤差較大，且為了計算之簡便，所假設之土壓力分布與實際狀況亦有相當之差異。本研究利用室內土槽進行一系列之側向樁載重試驗，以瞭解黏土中短樁受側向荷重後之力學行為。 由試驗結果得知，樁體承受側向荷重後，樁體側向位移將隨荷載歷時之增加而增加，但側向位移變化速率則漸趨平緩。然土壓力之分布則因置樁方式之不同而略有差異。 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，且位於黏土層淺層處之土壤側向抵抗能力較差，故本研究以增加土壤之剪力強度為控制主因，於樁周圍依邊長為3倍樁徑，高度為2倍樁徑之方形改良範圍回填改良土，以模擬混合攪拌方式之局部地盤改良。由試驗結果得知，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 theory of ultimate bearing capacity proposed by Broms is usually used for analyzing lateral bearing capacity of short pile. Although the assumptions of this theory are simple and convenient, the proposed earth pressure distribution is quite different to the reality. This research carried out a series of model pile tests to understand the mechanical behaviors of short pile under lateral loading in clay. The experimental results showed that the lateral displacement of the model pile under lateral loading increased with elapsed time. However, the distribution of earth pressure acting on the model pile in various cases is different due to the different pile installation methods. 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 performed a local soil improvement to increase the shear strength of soil near the surface. The cement treated soil is embedded around the pile with dimension of 3D×3D in plain area and 2D in depth. The experimental results showed that local soil improvement with a small quantity of cement material decrease the lateral displacement of the pile significantly.