Evaluating the effectiveness of foam mortar as a lightweight fill for reducing foundation settlement on soft soils: a case study of Indonesian toll road projects

Evaluating the effectiveness of foam mortar as a lightweight fill for reducing foundation settlement on soft soils: a case study of an Indonesian toll road. The construction of toll roads on soft soil in Indonesia is associated with significant geotechnical challenges, primarily excessive and long-lasting settlement. Therefore, this study aims to evaluate the effectiveness of foam mortar as a lightweight fill to mitigate issues across three distinct toll road projects: Probolinggo–Banyuwangi, Kediri–Kertosono, and Semarang–Demak. The method used was comprehensive numerical analysis, focusing on assessing the magnitude and rate of subsoil compression and slope stability under different scenarios of varying embankment heights, soft soil depths, and soil improvement strategies, including prefabricated vertical drains and replacement. The results consistently showed that incorporating foam mortar significantly reduced settlement. An increase in foam mortar percentage in the embankment also led to a substantial decrease in compression magnitude. Optimal performance was observed with a mix of 75% foam mortar and 25% soil for high embankments. Furthermore, this study provided customized, efficient design solutions for each site. The trend indicates that foam mortar is a viable, cost-effective alternative to conventional methods. This is because the application enhances slope stability and ensures compliance with stringent settlement-rate criteria, offering a practical solution for infrastructure development on compressible soils.