坑中坑开挖对悬臂式支护结构侧移的影响分析

Influence of pit-in-pit excavation on lateral deformation of cantilever retaining structure

悬臂式支护结构比内撑式支护结构对变形更为敏感,坑中坑开挖将对悬臂式支护结构侧移产生较大影响。利用有限元计算程序,建立坑中坑有限元模型并作全面数值模拟研究,得到了坑中坑不同开挖位置、深度及大小对围护结构变形的影响规律,并探讨了相应的变形控制措施。结果表明:外坑围护结构最大侧移随坑趾系数的增大而减小,并且坑趾系数存在临界值,最大侧移随着深度比和面积比的增大而增大;围护结构侧移受深度比影响最大,坑趾系数次之,面积比最小;增大内坑围护结构刚度和入土深度对抑制外坑围护结构变形增大的作用不明显,相反,内坑设置支撑能起到显著的作用。

The cantilever retaining structure is more sensitive to the deformation than the internal bracing retaining structure. The excavation of pit-in-pit will bring great impact on the cantilever retaining structure. By using the finite element program to establish pit-in-pit models and to perform comprehensive numerical simulation studies, the deformation characteristics of the outer pit are studied in the cases of different positions, depths and areas of the inner pit excavation. Moreover, the measures to control the deformation are also discussed. The results show that the maximum lateral deformation on cantilever retaining structure increases with the decrease of pit toe coefficient which has a critical value. However, they perform completely opposite in terms of depth ratio and area ratio. The depth ratio has the greatest impact on the lateral deformation of cantilever retaining structure, while the area ratio has the least impact on it. The increase of the stiffness and embedded depth of cantilever retaining structure has no significant effect in inhibiting the increase of the deformation of the retaining structure of the outer pit. However, it performs completely opposite if the inner pit has internal bracing.