Structures constructed on collapsible soil are prone to failure under flooding. Agro-waste like rice husk ash (RHA) and its geopolymer (LGR), consisting of lime (L), RHA, water glass (Na2SiO3), and caustic soda (NaOH), present a potential solution to address this issue. RHA and LGR were mixed up to 16% to improve the collapsible soil. Samples were remolded at optimal water content and maximum dry density for strength and collapsible potential tests. Unconfined compressive strength, deformation modulus, and soaked California bearing ratio exhibit exponential improvement with the inclusion of LGR. Additionally, for comparison of microstructural characteristics, analyses involving energy-dispersive X-ray spectroscopy (EDAX) and scanning electron microscope (SEM) were conducted on both virgin and treated specimens. LGR resulted in the emergence of new peaks of sodium silicates and calcium silicates, as indicated by EDAX. The formation of H-C-A-S gel and H-N-A-S gel observed in SEM suggests the development of bonds among soil particles attributed to geopolymerization. SEM reveals the transformation of the inherent collapsible soil from a dispersed and silt-dominated structure to a reticulated structure devoid of micro-pores following the incorporation of LGR. A numerical model was constructed to forecast the performance of both virgin and stabilized collapsible soils under pre- and post-flooding conditions. The outcomes indicate an enhancement in the soil's bearing capacity upon stabilization with 12% LGR. The implementation of 12% LGR significantly resulted in a lower embodied energy-tostrength ratio, emissions-to-strength ratio, and relatively lower cost-to-strength ratio compared to the soil treated with 16% cement kiln dust (CKD). (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/

Challenges related to sustainability arise in all areas of human activity, but with a significant impact on the environment considering that the construction industry is held accountable for nearly one-third of the world's final energy consumption. The aim of this paper is to assess through the use of the Bob-Dencsak specific model a sustainable slope design taking into account environmental, economic, and safety variables. Thus, analysis was performed on four intervention works, two versions of reinforced concrete retaining walls and two versions of reinforced soil with a biaxial geogrid, which ensure the stability of a slope that serves as a base for an access road to an ecological landfill located in Alba County, Romania. The study's analysis points out that reinforced soil retaining walls are far more sustainable, providing the best sustainability indices, which is also supported by the impact of geogrids compared to reinforced concrete, thus resulting in the finding that reinforced concrete is less sustainable, achieving increases of up to 23% for embodied energy and 66% of CO2 emissions in the atmosphere. Finally, the paper provides recommendations for future research on the sustainability assessment of slopes, with the intention of reducing environmental damage, while keeping costs to a minimum.