Performance assessment of mechanically stabilised earth walls with sustainable backfills

The growing depletion of natural geomaterials has forced scientists and engineers to look for alternate sustainable backfill materials for large-scale practical applications. This study presents an experimental and numerical investigation of the performance of two sustainable backfills – namely, steel slag and construction and demolition waste (CDW) – for possible mechanically stabilised earth (MSE) wall backfill application. A detailed characterisation followed by the performance evaluation of the materials using extensive laboratory experiments, encompassing strength and drainage criteria, is presented. Results of the triaxial and California bearing ratio strength tests highlighted the superior performance of the sustainable backfill materials compared with that of the traditional backfill material. The adequate drainage capacity of slag and CDW reflected the encouraging possibility of utilising the materials as alternate backfills. Additionally, the strength enhancement options of sustainable backfills using geogrid reinforcement were evaluated. Finally, the feasibility of utilising the materials in a prototype MSE wall was investigated with the help of finite-element numerical analysis. The hardening soil model was used to capture effectively the non-linear stress–strain behaviour of these materials. Results obtained from finite-element analysis demonstrated multiple benefits of sustainable backfill materials. In comparison with the standard backfill, MSE walls with slag and CDW backfill demonstrated 56 and 70% reductions in horizontal wall displacements, respectively. Moreover, lower reinforcement strains were observed in walls with sustainable backfills.