樁基礎為各項工程中最常使用之基礎型式，當樁尖深植於較堅硬之土層或岩盤中，可承受上部結構物傳遞的荷重。但對於軟弱地盤而言，樁基礎抵抗側向荷載的能力會受到限制。為了符合基樁的使用性，必須將容許側向位移限制在某一限度，本文旨在探討置放地中橫樑的改良法對基樁側向位移之改良成效。 本研究採用有限元素軟體ABAQUS，模擬地中橫樑對側向載重樁產生側向阻抗的行為，探討不同尺寸之地中橫樑對改良成效的影響。本改良法以三個參數作為控制變數，即側向荷載、地中橫樑長度及地中橫樑厚度，將分析結果加以比較，歸納出最佳之改良方式。 由分析結果得知，隨地中橫樑長度及改良深度增加，地表處之樁身位移量也隨之減少，顯示在地表下的土層中置放地中橫樑時，可提供水平阻抗，有效減少樁身之側向位移。 Pile foundations are often used in large constructions. It can transfer the weight of structures directly to stiff layer or rock ground. However, the lateral resistances of piles in soft ground are limited. In order to conform to the practicability, the lateral displacement of pile must be restrained in a certain limit. This study focused on the treated effects of lateral displacement by underground crossbeam. The underground crossbeam can provide lateral resistance for pile which bears lateral load. The lateral bearing behaviors of pile in soft soil layer were analyzed by finite element method. To perform the numerical analysis, FEM based software named ABAQUS was used in this research. The analytic mode is governed by three parameters including lateral load, underground crossbeam’s length and underground crossbeam’s thickness respectively. Finally, the research showed the best mode of treatment by this numerical analysis results. The numerical results indicated that the lateral displacement decreases as the underground crossbeam’s length and depth increase. Installing underground crossbeam beneath the ground surface can provide suitable horizontal resistance and decrease the lateral displacement of the pile.
