Some road systems are unpaved due to limited governmental finance and fewer maintenance techniques. Such unpaved roads become vulnerable during heavy rainy seasons following restrained accessibility among cities and traffic accidents. Considering the circumstances, innovative and cost–effective approaches are required for unpaved roads. Microbially induced carbonate precipitation (MICP) is an emerging soil improvement technology using microbes to hydrolyze urea generating carbonate ions, and precipitates calcium carbonate in the presence of calcium ion. Induced calcium carbonate bonds soil particles enhancing stiffness and strength when the MICP reaction takes place within the soil system. This study introduces the use of microbes on unpaved road systems consisting of in situ lateritic soils. The MICP technology was implemented to improve soil strength through two approaches: surface spraying and mixing methods. A series of soil testing was performed with varying chemical concentrations to measure precipitation efficiency, strength, and quality for construction material and see the feasibility of the proposed methods. The laboratory test results indicated that the surface spraying method provided improved; however, it was highly affected by the infiltration characteristics of used soils. The mixing method showed promising results even under submerged conditions, but still required improvement. Overall, the proposed idea seems possible to apply to improving unpaved road systems in the lateritic region but requires further research and optimization.

Geocell is a reinforcing material in civil engineering that creates cell structures with multiple bands filled with fill materials inside the cells, thereby providing a ground reinforcement effect. Due to the easiness of the construction and application, geocell is suitable for rapid and temporary installation on unpaved roads. Geocells have various heights depending on manufacturing conditions. In this study, the behavior of sand reinforced with geocells having various heights was evaluated. The stress-settlement relationships of the test grounds were analyzed with a large-scale soil box system and a series of plate load tests. For additional analysis, the unit weight of the reinforced ground was measured. The performance of the system was quantified using a subgrade reaction modulus (K₃₀). As results, the K₃₀ of sand reinforced with 10 cm height geocell showed higher than that of unreinforced sand. However, for 20 cm and 30 cm height geocells, the measured K₃₀ were similar to or lower than that of unreinforced sand. It was discovered that as the geocell height increases, the compaction efficiency delivered to the fill material within the geocells decreases, causing lowering the engineering performance of the geocell-reinforced zone. At the end of the paper, possible scenarios of using geocells are discussed.