滑降式快速预支撑体系在超深基坑中的应用研究

Study on Application of Slide-down Rapid Pre-supporting System in Ultra-deep Foundation Pit

上海机场联络线4标华泾站基坑为超深基坑,分四个独立的区域进行开挖,其中4区基坑开挖深度达42.898 m。目前,超深基坑施工中最大的施工难点为基坑围护结构的变形控制。随着基坑开挖深度的不断加深,开挖工况也趋于复杂,一旦基坑变形过大,就会导致周边建(构)筑物和地下管线出现沉降、撕裂甚至损毁的情况,给超深基坑开挖施工带来极大的风险。伺服钢支撑具有安装快速、立即发挥支撑作用的优势,能极好地控制围护结构在开挖过程中的变形,因而在超深基坑开挖过程中得到广泛应用。滑升模板是混凝土结构中的一种活动成型胎膜,施工速度快,可极大地提高机械使用效率。基坑开挖施工过程中将二者有机地结合,研究了滑降式快速预支撑体系在超深基坑施工中地应用,介绍该体系的概况及施工工艺,分析其对基坑围护结构变形的控制效果,梳理总结分析其优势与不足。

The foundation pit of Huajing Station in Shanghai Airport Contact Line Bid 4 is excavated by 4independent zones, in which the excavation depth of the foundation pit in the fourth zone is 42.898 m. At present, the largest construction difficulty is the deformation control of the pit enclosure structure in the construction of ultra-deep foundation pit. With the continuous deepening of the excavation depth of foundation pit, the excavation situation also tends to be complex. Once the deformation of foundation pit is too large, it will lead to the conditions of causing the settlement, tearing and even damage of the surrounding buildings, structures and underground pipelines, which will bring the great risk to the excavation of ultra-deep foundation pit. The servo steel support has the advantages of rapid installation and immediately playing the supporting role, which can excellently control the deformation of the enclosure structure in the excavation process, thus is widely applied in the excavation of ultra-deep foundation pit. The climbing template is a movable molded fetal membrane in the concrete structure. Its construction speed is fast, which can greatly improve the mechanical service efficiency. The both are organically combined in the excavation process of foundation pit. The application of the slide-down rapid pre-supporting system in the construction of ultra-deep foundation pit is studied. The general situation and construction technology of this system are introduced. Its control effect of the enclosure structural deformation of foundation pit is analyzed. Its advantages and disadvantages are sorted out, summarized and analyzed.