为研究城市建筑密集区域深大基坑支护体系受力规律与安全支护技术,采用数值模拟手段对昆明轨道交通4 号线火车北站深大基坑开挖过程中支护体系受力变形规律开展研究,并结合现场监测手段对支撑伺服系统布置与应用效果进行论述分析。研究结果表明: 1)受支撑形式与支撑间距影响,内支撑体系中钢筋混凝土支撑轴力水平要大于钢支撑,支撑轴力呈折线分布,在混凝土支撑施作期间围护结构容易发生较大变形; 2)引入支撑轴力伺服系统,依据数值计算与设计要求,设定正确的轴力控制值,能更好地发挥支撑对围护结构的变形控制作用; 3)工程应用实际表明,支撑轴力伺服系统在深大基坑施工应用中效果良好,采用伺服支撑段围护结构累计水平变形要小于无伺服段,支护效果更为优越。

The force and displacement laws of supporting system of deep and large foundation pit of North Railway Station of Kunming Rail Transit Line No. 4 is studied by numerical simulation method. The layout and application effect of the support servo system are discussed and analyzed based on field monitoring. The results show that: (1) The reinforced concrete axial force level in the support system is larger than that of the steel support due to the support form and the support spacing, the axial force of support is distributed in a broken line, and the retaining structure is prone to large deformation during concrete support construction. (2) By introducing the supporting axial force servo system and setting the correct axial force value according to the numerical calculation and design requirements, the deformation control effect of the support on the retaining can be better exerted. (3) The engineering application shows that the support axial force servo system has a good application effect in deep and large foundation pits; the cumulative horizontal deformation of the retaining structure in section with servo support is less than that without servo support, which shows better supporting effect.