Abstract:To explore the post-construction settlement characteristics of foamed lightweight soil subgrade above a newly-built utility tunnel in soft soil area, relying on a municipal road project in Guangdong Province, a finite element model is established to simulate and analyze the settlement patterns of the subgrade and pavement under different post-construction periods, various tunnel burial depths, and different foamed lightweight soil densities. The results show that the post-construction settlement of the foamed lightweight soil subgrade mainly occurs within the first five years and stabilizes after 20 years, with the settlement distribution exhibiting a U-shaped pattern. As the burial depth of the utility tunnel decreases, the total pavement settlement reduces, and the settlement pattern transitions from a U shape to a W shape. The density of the lightweight soil significantly influences the settlement. When the density increases from 400 kg/m3 to 1 000 kg/m3, the post-construction settlement over 20 years increases by 43.4%. It is verified that the error between the simulated value and the measured value of the settlement at the center point of the pavement is 2.1% based on the field monitoring data of the post-construction 20 d, indicating that the numerical model has good prediction accuracy. It is recommended that the foamed lightweight soil with a density of about 600 kg/m3 be given priority in the project to balance the settlement control and material economy. The research findings can provide a theoretical reference for the design and construction of foamed lightweight soil subgrade above utility tunnel projects in soft soil regions.
