Research on Surface Deformation Law of Tianjin Soft Ground Overlapping Shield Tunnel Construction.

The construction of overlapping shield tunnels causes secondary disturbance to the ground, which will increase surface deformation. In order to study the law of surface deformation, this paper, relying on the Tianjin Metro Line 5 West Hotel Road-West Huanhu Road Interval and Line 6 West Huanhu Road-West Hotel Road Interval tunnel project, uses FLAC3D to numerically simulate the two excavation sequences and analyzes the measured data of 15 surface monitoring cross-sections to obtain the law of surface deformation of Tianjin soft soil layer overlapping shield tunnel construction. Research results indicate: (1) For the upper tunnel of this project, the reasonable range of advancing earth pressure to static earth pressure ratio α is 2.0~2.4, and the lower tunnel α should be 1. 2~1.6; (2) By fitting the measured surface data, it can be approximated that the settlement parameter k in the Peck formula obeys the distribution of N ~ (0.981, 0.230); (3) The shape and width of the surface settlement curve do not change with different excavation sequences, and the maximum surface settlement of excavation sequence 2 is increased by 0.8 mm; (4) With "first down, then up" excavation sequence, the width of the surface settlement trough is mainly affected by the lower tunnel. [ABSTRACT FROM AUTHOR]