软土地基大直径格形钢板桩围堰设计探讨

  目的]  大直径格形钢板桩围堰作为一种新型的围堰形式，不仅施工速度快，而且能够有效减少施工过程对海洋环境的污染。但目前在软土地基中大直径格形钢板桩围堰的设计方法还存在不足。  方法]  以我国某人工岛大直径格形钢板桩围堰为例，分别利用我国规范法、日本规范法和三维有限元弹塑性分析方法，对软土地基中大直径格形钢板桩围堰的稳定性问题进行了探讨。  结果]  研究结果表明:中国规范法计算得到的格外土体主、被动土压力小于日本规范法和有限元数值法。中国规范法假设大直径格形钢板桩围堰在倾覆破坏过程中结构旋转中心为格形钢板桩底部的前趾，而日本规范法和有限元数值法计算结果显示旋转中心位于格形钢板桩底部的非倾覆侧。不同旋转中心的选取方法导致了中国规范法计算的抗倾覆稳定性安全储备明显大于另外两种方法。  结论]  研究成果说明大直径格形钢板桩围堰在软土地基中的设计理论和方法还需进一步的研究和探讨。

Design of Large Diameter Cellular Sheet Pile Cofferdam in Soft Clay

  Introduction]  Large diameter cellular sheet pile cofferdam has been applied in practice recently due to the advantage of construction speed and less pollution to the environment. However, the design method of this cofferdam in soft clay is still in its infant.  Method]  Taking a large diameter cellular sheet pile cofferdam in an artificial island project in China as an example, this study focused on the potential problems in its design in soft clay. Three different methods were used to calculate the stability of the cofferdam. These methods included China′s code method, Japan′s code method and three-dimensional finite element method.  Result]  The results show that the earth pressures of foundation calculated by China′s code method are smaller than that of the other two methods. The overturning point is located at the un-overturning side of the cofferdam based on the results of Japan′s code method and the finite element method, whereas it is fixed at the front toe point of the cofferdam in China′s code. The safety factor of overturning failure by China′s code method is larger than that of the other two methods due to the different positions of the overturning points.  Conclusion]  This showed that more work of the design code method and theory should be conducted on large diameter cellular sheet pile cofferdam in soft clay foundation.