Performance evaluation of road embankment constructed using lightweight soils on an unimproved soft soil layer

• All samples satisfied the required target strength.
• The quality of the LWSs constructed was more or less satisfactory.
• The capillary rise phenomenon is related to the micro cracks inside LWS.
• The change of the LWS density was identified due to capillary rise.
• Based on settlement data, the LWS was successfully applied to reduce settlement.

This study was conducted to determine the performance of lightweight air-mixed soil (LWS) for expanded road construction for a short-term period without any soft ground improvement. The unconfined compression strength and capillary rise of lightweight soil and the settlement of the soft ground were measured. The unconfined compression strengths of the samples cured at the site for 1 or 5 months all satisfied the required target strength of 500 kPa. However, the homogeneity of construction was not verified because the values of strength depended on the sampling location. In addition, the strength difference between the laboratory and site samples was found to be approximately 19%, and thus, it should be considered for mixing design. The capillary rise was approximately 20 cm for 70 h because of the numerous tiny pores inside the lightweight soil. This phenomenon changes the density of the LWS. The relationship between the settlement time and the settlement of the soft ground underneath the expanded embankment was estimated by using the monitored data and back analysis. The current average consolidation ratio and the final settlement after 120 months were estimated to be approximately 32% and 4.5 cm, respectively. This settlement is much less than the allowable settlement of 10 cm. Consequently, the LWS used in this site was successfully applied to reduce settlement and ensure stability.