Abstract: This study evaluates the effectiveness of different roadbed treatment methods regarding the settlement and deformation of new and existing roadbeds during urban road construction. Using a municipal road project in Huadu District, Guangzhou as an example, a roadbed model including geogrid reinforcement and foam lightweight soil filler was established. The finite element analysis using ABAQUS software was used to conduct simulation with the roadbed construction improved with geogrid and foamed light weight soils. The effect of materials such as lightweight soil in controlling the settlement deformation of new and old roadbeds. Research results indicate that the application of the geogrids at the joints of the existing and new subgrades can significantly improve the stability of the subgrade. However, after reaching a certain number of laying layers, simply increasing the number of the geogrid laying layers has limited effect on improving displacement control. The foamed lightweight soil is used as a lightweight filler. As the filling thickness increases, its control effect on the settlement deformation of the new and old roadbed also becomes significant. Combining the advantages of the two treatment methods and considering the project cost factors, this study proposes a geogrid-foam lightweight soil joint treatment method by laying 3 layers of geogrids in the middle and lower parts of the old and new roadbed and filling the upper part. Foam lightweight soil with a thickness of 2m can effectively control the settlement deformation of new and old roadbeds and improve the overall stability and service life of the roadbed.

Key words: Municipal Roads, New and Existing Roadbeds, Geogrids, Foamed Lightweight Soil, Numerical Simulation