INTEGRATING STRUCTURAL PERFORMANCE AND ENVIRONMENTAL SUSTAINABILITY: INVESTIGATING BIO-TREATED SOIL FOUNDATIONS FOR STORMWATER RUNOFF MITIGATION AND PAVEMENT RUTTING RESISTANCE

Abstract

As urbanization and climate change grow more intense, demands for infrastructure solutions are increasing that can meet the twin goals of structural integrity and environmental sustainability. The traditional pavement foundation systems, mainly depending on cement-stabilized and mechanically-compacted subgrades, result in carbon emissions, hinder natural hydrological cycles, and are easily prone to rutting failures before the expected service life under growing traffic volumes and extreme temperatures. This paper provides a detailed investigation of the use of bio-treated soil foundations, in combination, for both stormwater runoff mitigation and improvement of pavement rutting resistance, using Microbially Induced Calcite Precipitation (MICP) and Enzyme Induced Calcite Precipitation (EICP). An integrated experimental and analytical approach, including triaxial shear testing, flexible wall permeameter analysis, wheel tracking simulation and life cycle assessment (LCA), was used to assess the mechanical, hydraulic and environmental performance of bio-cemented subgrade soils in a range of treatment intensities, soil gradations and climatic exposure scenarios. Results indicate that optimally bio-treated foundations show a 250-600% increase in the unconfined compressive strength (UCS) compared with untreated foundations, and one to two orders of magnitude reduction in hydraulic conductivity to allow for controlled infiltration and reduced peak discharge of runoff. The improved rutting resistance (measured by repeated load triaxial and wheel tracking tests) is a 2.5 to 4 times improvement in bio-treated specimens, and at 10,000 cycles, permanent strain accumulated was kept below critical levels. According to life cycle assessment, the global warming potential (GWP) is reduced by 35–55% for the whole life cycle of the materials compared to conventional Portland cement stabilization, and there are also positive impacts on eutrophication and ecotoxicity indicators. This paper suggests integrated design framework that brings together structural performance criteria with stormwater management goals, and proposes paradigm shift towards a bio-geotechnical infrastructure capable of being resilient, sustainable and hydrologically responsive.