Model Test on Approaching the Construction of Multi-Line Overlapping Shield Tunnels for Up- and Down-Crossing

Abstract

Multi-line overlapping shield tunnels have a complicated layout in the underground space, and the interaction mechanism between tunnels is very complicated. Based on the construction formation of multi-line overlapped shield tunnel with short-distance up- and down-crossing, indoor model tests were conducted to analyze ground settlement (caused by excavation unloading and stratum loss) and the longitudinal deformation law of existing tunnels based on the drainage method, according to the characteristics and control requirements of the short-distance construction of shield tunnels. The results show that as long as the construction strategy of first-down and then-up crossing is adopted, no sudden change in ground settlement would occur. Furthermore, neither the changes in transient settlements nor the final ground settlement would be too large, which is different from the strategy of first-up and then-down crossing; the first-up and then-down crossing strategy generally increases the curvature of the deformation curve of the existing tunnel, and the deformation of the existing tunnel will cause obvious repeated vibrations. This provides theoretical guidance for the design and construction of multi-line overlapped tunnels.

Mechanical responses of underground carriageway structures due to construction of metro tunnels beneath the existing structure: A case study

“…Apart from in situ monitoring, laboratory tests and numerical simulations are also useful methods (Boonyarak & Ng, 2015; Fang et al, 2022; Hu et al, 2022; Kim et al, 1998; Li et al, 2022; Liu, Wang, et al, 2022; Ng et al, 2013). Kim et al (1998) carried out a series of centrifugal tests and found that the existing tunnel section in the zone where a new tunnel traverses beneath it may generate a vertically compressive deformation as a result of the excessive thrust of jack for the newly built shield beneath it.…”