Abstract: The instability failure mechanism of rigid pile composite foundation under horizontal layered embankment has been studied in depth. However, regarding to the instability failure mode and failure mechanism of rigid pile composite foundation under super- high fill embankment and under inclined foundation conditions, there is still a lack of in-depth disclosure. Based on a project, the ABAQUS finite element software is used to establish a three- dimensional numerical model of the CFG pile composite foundation under the super-high fill load. Taking the stiffness damage of the pile into consideration, the failure mechanism of the CFG pile is studied. The results show that the concrete damaged plasticity model can simulate the mechanical properties of CFG piles well, and can reasonably display the actual process of pile stress release and internal force redistribution after pile failure, and the progressive damage of the CFG pile composite foundation can be analyzed by the software's damage output variable. Under the
effect of ultra-high filling load, the CFG pile on the inclined base may be bent or fractured, and its load-bearing characteristics and failure mode are quite different from those of horizontal layered embankment, which is represented by the bending moment of the central pile of the embankment. The shearing force is relatively large, and the bending and shearing damage of the pile is more likely to occur which is worth attention during design. The bending moment and shearing force of the pile on the left side of the embankment are generally smaller than that of the central pile, and is of less possibility of first damage to it.

Key words: CFG piles, damage model, inclined substratum, numerical analysis, failure mode

摘要： 对一般水平成层路堤下刚性桩复合地基的失稳破坏机理已有较为深入的研究，但对倾斜地基下高填方路堤荷载作用下刚性桩复合地基的失稳破坏尚缺乏深入揭示。依托某工程，对高填方荷载作用下倾斜基底CFG桩复合地基进行三维数值分析，研究考虑桩体刚度损伤的CFG桩复合地基的破坏机理。结果表明：混凝土塑性损伤模型能较好地模拟CFG桩的力学性能，能较合理地还原桩体破坏后桩身应力释放-应力再分布的实际过程，且可通过损伤输出变量分析CFG桩复合地基的渐进破坏过程。在高填方路堤荷载作用下，倾斜基底CFG桩的受荷特点和破坏模式较水平成层路堤有较大差异，表现为路堤中心桩所受弯矩和剪力较大，较易发生桩体的压弯破坏和剪切破坏，在设计中应予以重视，路堤左侧桩所受弯矩和剪力总体上小于中心桩，先发生破坏的可能性不大。

关键词: CFG桩, 损伤模型, 倾斜基底, 数值分析, 破坏模式