Effects of the artificial solidified crust on ground settlement during full scaffold construction in a coastal region

The full scaffold construction method is widely used in cast-in-place box beam construction and is especially sensitive to foundation settlement in soft soil areas, which can significantly impact project quality. Based on the Zhejiang Shiyitang Expressway project, this study proposed a combination of superficial ground treatment and preloading method to reduce costs and improve construction efficiency. An artificial solidified crust layer (ASCL) with a depth of 1.5 m was constructed using in-situ solidification technology, achieving a bearing capacity of 180 kPa. Settlement, pore water pressure, and lateral displacement at various depths were monitored during the foundation preloading, scaffold preloading, and cast-in-place box beam loading stages through in-situ testing and numerical modeling. The ground settlement 30 days after concrete casting was 15.4 mm, with most of the settlement occurring during the foundation and scaffold preloading stages. The ASCL was included in the additional stress calculation, resulting in a 27% reduction in total settlement compared to conditions without the ASCL. The influence of permeability coefficient, soil compression modulus, loading mode, and load application area was analyzed using the validated numerical model. The final settlements were found to be similar for soils with varying permeability coefficients, indicating that the superficial ground treatment method is suitable for different soil types. The "effective range" of foundation preloading refers to the width between the bridge web and the bridge pile foundation.