超大面积深基坑盆式开挖的工程实例分析

基坑回弹变形是基坑开挖卸载过程影响基坑安全较大的因素之一。基坑回弹量与卸荷量、基坑面积、支撑和围护结构等方面有关，基坑回弹量过大时，带动立柱桩上抬，将降低混凝土内支撑的承载力或使钢支撑失稳破坏，超大型基坑回弹变形尤其明显。除基坑支护结构的针对性措施外，通过基坑土方开挖工序的优化，也可以达到降低基坑回弹量的目的。结合上海宝山区某全地下污水厂超大面积深基坑工程实例，分析盆式开挖方式对超大面积深基坑回弹的影响。最终计算及实测数据表明，由于底板提前分块形成，充分发挥了工程抗拔桩的作用，基坑回弹变形量显著减小。

Analysis of Engineering Examples of Super Large Area Deep Basin Excavation

The rebound deformation of the foundation pit is one of the factors that greatly affect the safety of the foundation pit during the unloading process of excavation. The rebound amount of the foundation pit is related to the unloading amount, excavation area, support and enclosure structure, etc. When the rebound amount of the foundation pit is too large, it will drive the column piles to lift up, which will reduce the bearing capacity of the concrete internal support or cause the steel support to lose stability and damage. The rebound deformation of super large foundation pits is particularly obvious. In addition to targeted measures for foundation pit support structures, optimizing the excavation process of foundation pit earthwork can also achieve the goal of reducing the rebound amount of the foundation pit. Based on the example of a super large area deep foundation pit project of a fully underground sewage treatment plant in Baoshan District, Shanghai, this paper analyzes the impact of basin excavation method on the rebound of the super large area deep foundation pit. The final calculation and actual measurement data indicate that due to the early block formation of the bottom plate, the role of the engineering anti pull pile is fully utilized, and the rebound deformation of the foundation pit is significantly reduced.