Investigating the Response Characteristics of Elevated Bridge Piles during Twin Stacked Shield Tunnel Excavations

To investigate the cumulative impacts of excavating twin stacked shield tunnels on the internal forces and deformations at forward target points and the effects of twin tunneling, this study employs a two-stage theoretical analysis method rooted in practical engineering and integrates numerical simulations to examine the response characteristics of nearby bridge piles to internal forces and deformations resulting from the excavation of stacked shield tunnels. First, by leveraging the Mindlin solution and accounting for dynamic spatiotemporal cumulative effects, analytical solutions for the three-dimensional displacement field and stress field of the surrounding rock during shield tunneling are derived and validated. Second, by employing the Pasternak foundation beam theory, theoretical solutions for the internal forces and deformations of nearby bridge piles associated with shield tunnels are presented. Last, considering the twin tunneling effects of excavating stacked tunnels, a maximum deflection correction parameter, η, is proposed for nearby bridge piles of twin stacked shield tunnel excavation to effectively rectify errors arising from a simple superposition of theoretical solutions. The findings provide a certain theoretical foundation and data support for the safety risk assessment of nearby bridge pile engineering during the excavation of twin stacked tunnels.