Abstract:

The influence on the operating Metro lines induced by the construction of adjacent foundation pits should be strictly controlled so as to ensure the safety of the existing Metro lines. The support design and construction program of the deep foundation pit and the deformation monitoring results of the existing Metro tunnel are analyzed and summarized, with the construction of a deep foundation pit adjacent to an existing Metro tunnel in Guangzhou as an example. Conclusions drawn are as follows: 1) The construction of the deep foundation pit adjacent to the existing Metro tunnel should be strictly controlled. Rational support design and construction program of the deep foundation pit are fundamental for the structural safety of the existing Metro tunnel. 2) Sectionbysection construction method is adopted for the foundation pit. Support consisting of doublerow piles and bracing is adopted for some sections of the foundation pit, which not only improves the rigidity of the support, but also is convenient for the cutting of the foundation pit. Soil bench is kept during the cutting of the foundation pit, which can effectively control the deformation of the doublerow piles and in the end can minimize the influence on the existing Metro tunnel. 3) The analysis on the deformation monitoring results shows that the deformation of the existing Metro tunnel meets the requirements of relevant standards and that the safety of the foundation pit is guaranteed. 

Key words: operating Metro tunnel, support design, foundation pit, construction, deformation control, monitoring analysis