Abstract: To obtain the density parameters for the settlement of pavement over soft soils with the replacement of foamed lightweight aggregate, a finite element numerical model was established. The first-class highway reconstruction project of a national highway is presented in this paper to study the soft subgrade load reduction and replacement with foamed lightweight aggregate. The maximum settlement of the foamed lightweight aggregate with a density between 300 kg·m^-3 and 700 kg·m^-3 30 days after the replacement was also studied. The maximum settlement values of 30 days after pavement replacement under different densities of lightweight aggregates were 15.8mm, 23.1mm, 25.4mm, 32.3mm and 37.8mm, respectively. The positions of the observed maximum settlement were all at the center point of the roadbed; secondly, under the premise of considering quality and safety, it was determined that the lightweight aggregate density of 400 kg·m^-3 was the most cost-effective product to meet the requirements of engineering construction. In addition, numerical analysis shows that under the same lightweight aggregate density, the post-construction settlement of the top of the pavement can be effectively reduced with the increase of the thickness of the foamed lightweight aggregate.

Key words: Replacement and Backfills, Road Settlement, Foamed lightweight Aggregate, Density