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研究目的:坑中坑是工程中应用较为普遍的一种非对称基坑型式,目前相关的理论研究较少,工程设计中往往凭经验确定其影响范围。本文结合南京青奥轴线地下工程上部悬臂、下部设置内支撑的基坑工程,通过有限元计算分析,探讨坑中坑型式非对称基坑围护结构的变形和土压力分布特征,旨在为工程设计提供参考。研究结论:(1)内、外坑围护距离以及内坑开挖深度对坑中坑围护结构变形和受力影响显著;(2)随着内、外坑围护距离的不断缩小,内坑围护向坑外的变形不断减小直至偏向坑内,内坑围护外侧土压力可按外坑为地表计算且考虑一定的安全系数;(3)随着内坑开挖深度加大,内坑围护偏向基坑外侧位移加大;内坑未开挖或开挖较浅时,坑底以上外坑围护结构侧向土压力介于主动土压力和静止土压力之间;内坑开挖较深时,坑底以上土压力接近主动土压力,直至坑底逐步接近静止土压力;(4)本研究结果对类似基坑工程的分析与计算具有参考价值。
Research purposes: The pit in the pit is a kind of asymmetric pit commonly used in engineering. There are few relevant theoretical researches at present, and its influence scope is often determined empirically in engineering design. In this paper, based on the Nanjing Canoe axis underground engineering cantilever, the lower part of the inner support of the foundation pit project, through the finite element analysis of the pits pit type asymmetric excavation envelope deformation and earth pressure distribution characteristics designed for engineering Design for reference. The conclusions are as follows: (1) The distance between the inner and outer pits and the depth of the inner pits have a significant influence on the deformation and the force of the pits. (2) With the continuous shrinkage of the inner and outer pits, The deformation of pits surrounding the pits decreases continuously until they deviate into the pits. The earth pressure outside the pits can be calculated according to the outer pits and taking into account a certain safety factor. (3) With the deepening of the inner pits, When the inner pit is not under excavation or shallow excavation, the lateral earth pressure of the retaining structure above the bottom of the pit is between the active earth pressure and the rest earth pressure. The inner pit open When digging deeper, the earth pressure above the bottom of the pit approaches the active earth pressure until the bottom of the pit gradually approaches the resting earth pressure. (4) The results of this study are of reference value for the analysis and calculation of similar foundation pit engineering.