二级联合支护结构深基坑整体稳定性分析

Analysis of Overall Stability of Combined Retaining Structures in a Deep Excavation

深基坑工程中由于设计变更而导致部分区域开挖深度加大,因此在工程实践中出现了具有不同墙顶标高的二级联合支护结构,而现有的常规分析软件难以直接对此类深基坑进行整体稳定性分析。基于有限元强度参数折减法,运用大型有限元软件ABAQUS对这种特殊支护结构进行了整体稳定性分析。采用土体最大位移与开挖深度的比值发生突变作为基坑失稳的判别依据,重点分析了内侧挡墙插入深度,支撑刚度和不同支撑布置形式对这种支护结构基坑的整体稳定性的影响,得到了若干有意义的结论。最后,提出了可直接利用常规软件进行分析的简化计算模型,并基于不同典型土质给出了相关系数的取值范围,可为采用类似支护结构的基坑整体稳定性分析提供有益参考。

The unexpected change often takes place in the design of deep foundation pit, which may lead to a larger depth of excavation in some parts of the foundation pit. So a special combined supporting system with different top elevation for each retaining wall is applied in some practical projects. Because the overall stability of this kind of retaining structure can not be analyzed by using the common design software directly, a FEM software ABAQUS based on the concept of the shear strength reduction was applied in the analysis. The abruptness of the curve, which says how the maximum displacement varies along with the factor of the shear strength reduction, was used as the instability criterion of the pit. And the effect of many factors on the overall stability of the retaining structure such as the depth of the inner retaining wall, the stiffness and the distribution of struts was analyzed systematically. Finally, a simplified model for the analysis of the combined supporting system was presented so that the stability of such kind of retaining structure could be analyzed directly by using a common software. The range of the relevant parameter value was also offered based on the computational results from some typical soil, which can be used as a helpful reference in the similar projects.