Abstract:To further study the impact of the reconstruction of the Huangpu River flood control wall on the underlying existing tunnels, taking the special maintenance project of the embankment in the Puxi Expo Park section of the Huangpu River, directly above the South Xizang Road Tunnel as an example, two reconstruction schemes such as the secant pile flood control wall and the typical “front slab, rear pile” flood control wall in Shanghai are proposed for analysis and comparison. The Plaxis finite element software is used to simulate the impact of the two flood control wall construction schemes on the underlying tunnel. Combined with a comparative analysis of monitoring results during the construction period, the findings indicate that the secant pile flood control wall can more effectively reduce the impact on the underlying existing tunnel, while solving the problem that the prefabricated piles cannot be constructed due to deep obstacles beneath the site compared to the typical “front slab, rear pile” flood control wall in Shanghai. When the pile foundation of the newly constructed secant pile flood wall is 6.2 m from the tunnel crown and the maximum excavation depth is 2.4 m, both finite element simulations and actual monitoring results show that the maximum displacement of the tunnel directly below the flood control wall is about 1 mm, which is significantly less than the tunnel deformation alarm threshold of 1 cm, indicating a minimal impact on the tunnel. The Plaxis finite element simulation results can provide valuable references for the reconstruction of flood control walls above tunnels during the scheme design phase.
