中文摘要：

基于土体塑性极限平衡原理，以6自由度圆形基础为研究对象，利用非线性有限元分析软件Abaqus，对圆形基础极限承载能力进行了数值分析．研究结果表明：三维荷载空间中，复合加载模式下竖向荷载对海床地基破坏包络面的形状和大小的影响比较明显；圆形基础对应的破坏包络面曲线比二维条形基础对应的包络面曲线圆滑，包络面曲线不存在斜率突变段；圆形基础上水平荷载分量与力矩荷载分量对破坏包络面形状和大小影响较强，而扭矩荷栽分量对破坏包络面形状和大小影响较弱．同时，提出了荷载分量对复合加载模式下海床土体破坏包络面方程的影响判别公式．

英文摘要：

Based on the plastic limit equilibrium theory of soil, the ultimate bearing capacity of circular footing with 6 degrees of freedom（DOF） was analyzed by finite element analysis software of Abaqus. The results show that the vertical loading has remarkable effect on the shape and amplitude of the failure envelope of seabed under combined loading. The failure envelope of circular footing in three-dimensional loading space is more round than that in two-dimensional loading space, and the slope of failure envelope has no sharp change. The horizontal loading and moment loading have strong impact on the shape and amplitude of failure envelope, while the torque loading has slight impact on the failure envelope in three-di- mensional loading space. A critical formula was proposed to estimate the effect of loading components of combined loading on the failure envelope of seabed.