近接既有结构深大基坑隆起变形控制——以天津地铁5号线思源道站接建地下空间工程为例

Heave Deformation Control Method of Large-scale Deep Foundation Pit Adjacent to Existing Structure:Taking the Underground Space Project Connecting to Siyuandao Station of Tianjin Metro Line 5 as an Example

现行基坑支护规范抗隆起主要验算支护结构的稳定,无法满足拓建工程对基坑隆起变形的严格要求。从力学平衡和刚度控制的角度,阐明了深大基坑隆起的力学机理和隆起荷载的计算方法,提出了控制基坑隆起的新途径。研究表明:基坑隆起荷载与支护结构的入土深度、基坑深度、基坑宽度、土体内摩擦角和土体重度等因素有关;将基坑隆起问题转化为坑底加固土层的平衡问题,可以作为拓建工程基坑隆起控制的计算方法;坑底土体刚性加固和抗拔桩是控制基坑隆起变形的重要措施,坑底加固和抗拔桩应在基坑开挖前实施。

Anti uplift in the current foundation pit support code is mainly used to check the stability of the support structure,which cannot meet the strict requirements of the extension project on the upheaval deformation of the foundation pit.From the point of view of mechanical balance and stiffness control,the mechanical mechanism of deep and large foundation pit heave and the calculation method of uplift load were expounded,and a new way was put forward to control the uplift of foundation pit.The results show that the uplift load of foundation pit is related to soil penetration depth of supporting structure,depth and width of foundation pit,the internal friction angle and the weight of soil mass.The method of load balance of soil layer,which transforms the deformation of pit bottom into structural balance problem,can be used as the calculation method of foundation pit uplift control in extension engineering.The rigid reinforcement and anti pulling pile of the soil at the bottom of the pit are put forward to control the uplift deformation of the foundation pit,but this method should be implemented before the excavation of the foundation pit.