New Selection Process for Retaining Walls Based on Life Cycle Assessment and Economic Concerns

Abstract

Earth-retaining walls (ERWs) are widely used structures in civil engineering, a field known for their substantial environmental impact. However, the current practice of selecting ERW types for a project often neglects environmental concerns. To address this issue, this study proposes a novel process to enhance the rationality of ERW selection. It involves assessing the performance of commonly used ERW types in terms of both environmental issues and economic considerations. The proposed process relies on calculating a total cost (TC), which incorporates the costs of two crucial environmental indicators: carbon dioxide (CO2) emissions and cumulative energy demand (CED), evaluated using life cycle assessment (LCA), in addition to considering the traditional construction cost of the ERW. By determining the TC for various retaining wall options, engineers can identify the optimal ERW type for a specific project. To validate the effectiveness of this environmental-economic approach, a case study was conducted comparing two ERW types: the conventional concrete-reinforced retaining wall (CRRW) and the geosynthetic-reinforced retaining wall (GRRW). The study evaluated structures constructed at four different heights, ranging from 3 m to 6 m. The results demonstrate that the GRRW is the optimal option, offering a lower TC than the equivalent wall conventionally built with reinforced concrete across all evaluated heights. However, the difference in TC between the two ERWs is more pronounced for taller walls. At a height of 3 m, the total cost ratio between the CRRW and the GRRW is moderate at 1.2, while it substantially increases to 2.5 at a height of 6 m. In conclusion, the proposed process was effectively applied to the case study, providing valuable insights into the assessment of earth-retaining structures from both environmental and economic perspectives. It can assist engineers in prioritizing and selecting the most sustainable and cost-effective ERW type for a specific project.