Numerical Prediction on Impact of High-Rise Building Construction Above Existing Underground Twin Tunnels

The rapid expansion of urban infrastructure has necessitated the construction of high-rise buildings in close proximity to underground tunnels, posing significant challenges to their structural integrity. This study investigates the effects of excavation and building construction on existing underground tunnels using finite element analysis in PLAXIS 2D. Different construction stages, including excavation with braced cuts and subsequent loading from high-rise buildings with load intensities of 25, 75, 150, 250, 450, 750, 1150, 1650, and 2650 kPa corresponding to building load above an existing underground twin tunnel, are analysed. The position of the excavation trench with respect to the central point of the twin tunnels is varied to observe maximum deformations at each position. Results reveal that construction of buildings above the twin tunnels significantly affects their stability. Excavation-induced stress redistribution leads to localized deformations, which are further amplified by building loads. Under a 2650 kPa load, maximum deformations of 25.69 mm and 19.88 mm were observed in the left and right tunnels, respectively. However, at a distance of 24 m from the central point of the tunnels, the maximum deformation under a superstructure load of 2650 kPa has reduced to less than 10 mm. This research contributes to safer urban planning by providing practical guidelines for constructing high-rise buildings near and above existing underground tunnels.