为探讨土钉支护基坑的变形特性与荷载传递机理，结合土钉支护的施工特点，采用FLAC 3D建立了考虑分步开挖与土钉支护的基坑计算模型，分析了基坑侧向变形、土体剪应变增量及土钉轴力传递特性．结果表明：逐级放坡开挖基坑的最大侧向变形深度位于下部斜坡，阳角是平面内变形的不利位置，放坡平台对于控制基坑变形具有积极作用；拉伸破坏与剪切破坏是坡面破坏的主要形式，采用剪应变增量可以直观判断基坑边坡滑动面的变化规律，土钉加固作用使滑动面有向土钉末端移动的变化趋势；土钉轴力沿长度分布与土钉深度位置相关，一般呈现中间大两端小的特点，土钉轴力最大值位置与潜在滑动面位置基本一致．

In order to investigate the deformation characteristics and load transfer mechanism of deep excavation, a numerical model considering the process of stepped excavating and soil nailing was established by FLAC 3D. The lateral displacement of excavation surface and outside soil, the shear strain increment of soil, and the axial force distribution of nail were analyzed. The results show that, the maximum lateral displacement appears close to slope toe, meanwhile, outside corner is the most disadvantageous location of deflection, and the multilevel platforms have positive effects on controlling soil deformation. Tensile failure and shear failure are the two main failure modes of excavation slope. The location of potential sliding surface can be indicated by shear strain increment contour, and the location moves toward the outside end of soil nail due to soil nail reinforcement effects. The maximum axial force of soil nail appears near the middle and the relative minimum value near the two ends, and the distribution of maximum axial force agrees well with the potential sliding surface.