Sustainability Assessment of Two Alternate Earth-Retaining Structures

Abstract

This study presents the sustainability assessment of two alternate earth- retaining structures: cantilever retaining wall and mechanically stabilized earth (MSE) wall over their respective life cycle period. Sustainability evaluation of both retaining structures is performed based on three commonly employed assessment pillars, which are environmental, economic, and social impacts. The environmental impact assessment of cantilever wall and MSE wall is performed by considering various life cycle stages of both systems that cover raw material acquisition, construction, maintenance, and demolition efforts. For design purposes, total wall span, wall height, subsurface soils and backfill soil profiles of both earth-retaining structures are considered to be the same. Technical designs of both earth-retaining structures are carried out based on limit equilibrium method, and it is found that both earth-retaining structures are safe against failure criterion, such as, sliding along the base, overturning about the toe, and bearing failure capacity. The life cycle assessment (LCA) is conducted using SimaPro 8.0 software, related databases and impact assessment methods. It is observed that potential environmental impacts, such as global warming, acidification, and smog are primarily influenced by the concrete and steel production along with the diesel used for transportation and on-site machinery due to mineral extraction, refining, and required energy inputs for processing. Based on the LCA, it is assessed that MSE wall is more environmentally sustainable than cantilever retaining wall. Subsequently, economic evaluation and social impact analyses are conducted for the two retaining structures and the results are compared. It is concluded that the mechanically stabilized earth (MSE) wall is overall more sustainable than the cantilever retaining wall in terms of environmental, economic, and social aspects over their entire life cycle.