圆形深基坑围护结构优化设计研究

为深入研究圆筒状地下连续墙的内力和变形特征,建立实际风井工程的三维有限元力学模型,重点分析不同地下连续墙接头刚度、分幅形式以及坑底加固混凝土标号等因素对施工期整个围护结构内力和变形的影响。研究成果表明:1)地下连续墙接头刚度的变化对圆形围护结构的受力和变形的影响不甚明显,接头刚度越小,地下连续墙位移稍许增大,内力变化很小;2)地下连续墙分幅数的影响较为明显,槽段设置24幅与15幅相比,围护结构产生的变形和内力较小;3)工作井底板下部混凝土标号越高,墙体所受的内力和变形越小,并由此提出合理的支护技术参数和措施。所得结论表明,风井基坑在土体开挖及盾构破井过程中的稳定性符合安全要求。

Research on Optimization Design of Retaining Structures of Deep Cylindrical Foundation Pit

A three dimensional finite element model is established for a ventilation shaft of Metro works, so as to study the internal force and deformation characteristics of the cylindrical diaphragm wall. By using the above model, the author analyses the effects of different joint stiffness of diaphragm wall, different segment forms of diaphragm wall and different strength grades of concrete on the deformation and internal force of the retaining structure during the construction period. The result shows that: 1) the impact of joint stiffness on the diaphragm wall is not obvious, the horizontal displacement increases slightly as the joint stiffness decreases, while the internal force of the diaphragm wall varies very little; 2) the effect of different segment forms of the diaphragm wall is more obvious; 3) compared to the 15 segment shaped retaining structure, the deformation and internal force of retaining structure with 24 segments appear smaller; 4) the deformation and internal force of retaining structure vary little when the grade of the concrete below the floor of the shaft becomes higher. According to the result, the author puts forward the reasonable supporting parameters and measures. The conclusions drawn show that the stability of the foundation pit of the ventilation shaft during excavation and diaphragm wall breaking by shield machine can comply with the safety requirements. 