Improving the engineering and mechanical properties of marine clay (MC) by modifying it with soda residue (SR) and fly ash (FA), and stabilising with cement and /or lime to create Soda residue-Fly ash stabilised soil (SRFSS). Using the orthogonal design, the mechanical properties of SRFSS were analyzed, recommending a basic proportion of 70% SR + 20% FA + 10% MC. Results showed SR significantly impacted optimum water content (OWC), unconfined compressive strength (UCS), and water absorption quality. FA influenced the maximum dry density (MDD), while cohesion (c) was mainly affected by lime and cement. Cement had a higher unit contribution rate to mechanical indices than lime, except for MDD and OWC. The excellent properties of SRFSS were derived from good gradation and the cementation action of the materials. This research provides a solution for improving MC properties and promoting solid waste reutilisation.

Cyclic loading may induce changes in the geomechanical behaviour of materials that should be characterised. This work studies the impact of the number of loading cycles on the mechanical behaviour of a fibre-reinforced stabilised soil focusing on its behaviour before failure (yield surface). To this end, an experimental testing program based on triaxial tests was performed on samples not subjected to a cycling loading stage, as well as on samples previously subjected to a cycling loading stage varying the number of loading cycles from 1,000 to 100,000. The results were studied in terms of the accumulated permanent axial strain and the yield surface of the composite material. It was observed that increasing the number of loading cycles led to a rise in the accumulated permanent axial strain and in the undrained resilient modulus. The results also showed an expansion of the yield surface during the first 1,000 loading cycles (the yield occurs later due to the partial mobilization of the tensile strength of the fibres during the cyclic stage) but its shape is maintained. The results also showed a progressive reduction in the yield loci with the increase in the number of loading cycles, reflecting the greater degradation of the solid matrix induced by the accumulated permanent axial strains.

When a soil is subjected to cyclic loading, there are changes in the material's geomechanical behaviour that need to be characterized before safely designing any future projects. In terms of cyclic loading, it is important to characterise not only the failure of the soil but also its behaviour before failure, in particular the yield point and the elastic behaviour of the material. This study examines the effects of the number of loading cycles on the behaviour of a chemically stabilised soft soil with a particular focus on the yield surface. To this end, a series of triaxial tests were performed on specimens, previously or not subjected to a different number of loading cycles (1,000-100,000). The results were analysed in terms of the evolution of accumulated permanent axial strain, the yield surface and stress-strain behaviour. It was observed that an increase in the number of loading cycles promoted: an increase in the permanent axial strain, an increase in the undrained resilient modulus, a shrinkage of the yield surface but its shape is maintained, and there is a small increase in the peak strength of the stabilised soil explained by the strain hardening effect induced by the cyclic loading.