某特深基坑考虑支护结构与土体共同作用的三维有限元分析
3-Dimensional FEA for the interaction between supporting structure of excavation and soil in a very deep pit
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摘要: 某特深基坑设计尺寸达到69m×50m×50m,且施工场地地质条件较差,基坑变形控制严格,用普通近似方法分析和设计有较大的难度。为了准确了解基坑支护结构的内力和变形情况,确保工程安全,本文对该基坑进行了施工全过程的三维有限元弹塑性分析和模拟,并详细说明了其具体实现方法。有限元分析中分别考虑了支护结构和土体之间的相互作用问题,以及各种开挖方案、降水方案对基坑变形的影响,并对各种关键参数进行了参数敏感性分析和讨论。对比各种分析结果,考虑共同作用和不考虑共同作用基坑变形相差达到10倍,支护结构内力相差达到1.5倍。同时,不同开挖方案及降水方案对变形和内力也有着重要影响,各方案之间最终差别甚至可以达到1倍以上。分析结果说明,对于这类复杂工程,进行考虑结构与土体共同作用的施工全过程三维有限元分析和模拟是完全必要的。Abstract: The size of a very deep pit is about 69 m×50 m×50 m and it is difficult to be analyzed with traditional approximate method. In order to reveal the deformation and internal force of its support structure, spatial nonlinear finite element analysis is carried out in which the excavation process is considered. The interaction between the excavation support and the soil, the difference between various excavation scheme, the influence of groundwater lowering and sensitive analysis of critical parameters are discussed in detail. The numerical results show that the deformation of the continuous concrete wall with interaction effect will be 10 times of that without interaction effect, while the difference of supporting forces between the two cases will be 1.5 times.At the same time, the excavation scheme and ground water lowering are also important for the deformation and internal force of the support. The analysis results show that investigation of the interaction between soil and structure and simulation of excavation process are necessary in such complex problems.
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