混凝土支撑伺服系统在某深基坑工程的应用研究

Practical research of concrete strut with automatic axial force compensation system in a deep excavation project

为有效减小软土基坑的变形,工程中将液压千斤顶融入混凝土支撑结构中,形成了混凝土支撑伺服系统(CAC)。为研究CAC的实践效果,对CAC的结构组成和工作机理进行了阐述和分析,并以前滩21号地块基坑工程为例,通过对围护墙水平变形和支撑轴力实测数据的研究分析,总结了有无CAC两种情况下围护墙的变形规律和支撑轴力的特征。该项目采用CAC的围护墙实测水平变形仅为基坑开挖深度的1.4‰,满足了软土特级基坑的微变形控制要求。实践分析表明,CAC大大提高了混凝土支撑的实际刚度,有效解决了混凝土收缩、徐变等造成的刚度损失问题,显著减小了开挖面以上围护墙的变形发展。CAC适用于周边环境保护要求高、基坑平面尺寸宽大或形状不规则的软土基坑,应用前景广阔。

To effectively reduce the deformation of soft soil excavation, the concrete strut with automatic axial force compensation system(CAC) was developed by integrating hydraulic jack into concrete strut and applied in excavation projects. To study the practical effect of CAC, the structure composition and working mechanism of CAC were elaborated and analyzed. Based on the analysis of monitored horizontal wall deformation and strut force in Qiantan 21# project, the laws of retaining wall deformation and characteristics of strut force in both cases with and without CAC were studied. In this project, the monitored horizontal deformation of retaining wall was only 1.4‰ of excavation depth, which reached the micro-deformation control requirements of soft soil excavation with special protection level. It shows that the application of CAC could greatly improve the stiffness of concrete strut, compensate the stiffness loss caused by shrinkage or creep of concrete and reduce the deformation development of wall above excavation face effectively. CAC is suitable for soft soil excavations with high environmental protection requirements, large plane dimensions or irregular shapes, and has broad application prospects.