Reducing the environmental impact of construction through use of geosynthetics

The changing climate and damaging effects of CO2 on the environment has led to awareness throughout the construction industry of the need to deliver more sustainable solutions. The use of geosynthetics as a sustainable construction solution was demonstrated by the Waste and Resources Action Programme (WRAP) in a report entitled Sustainable Geosystems in Civil Engineering Applications (WRAP, 2010). The WRAP report presented a series of case studies in which geosynthetic solutions provided both cost and CO2 savings in comparison to non-geosynthetic solutions. However, in what is a huge field the report concentrated on specific areas relative to the calculation methods or on the potential construction applications. This EngD research built on this work by WRAP and aimed to establish a rigorous framework for the comparison of CO2 emissions between geosynthetic and non-geosynthetic solutions. This EngD research reviewed CO2 calculation methodologies and techniques to produce a rigorous framework that could be adopted in comparative CO2 studies between geosynthetic and non-geosynthetic solutions. It was demonstrated on three case studies looking at geosynthetics in the function of containment, drainage, and reinforcement, highlighting the possible CO2 benefits of employing geosynthetics. The development of the case studies and framework highlighted the need for accurate embodied carbon data. There was an absence of geosynthetic specific embodied carbon values in the commonly employed databases. The EngD research sought to address this and through some experimental work in collaboration with geosynthetic manufacturers calculated embodied carbon values for four types of geosynthetics

Comparison of carbon dioxide emissions for two landfill capping layers

Geosynthetics are commonly employed in landfill applications to provide containment in the capping layer, also referred to as a cover system. This paper presents a case study that compares the CO2 emissions produced from a compacted clay landfill cap as compared to one incorporating geosynthetics. The Life Cycle Analysis boundaries set for this case study were of cradle to end of construction, and including all processes from sourcing of materials through to the end of construction. As-built data provided by the contractors and manufacturers was used to calculate the carbon footprint of each solution. Comparison showed the geosynthetic solution to be more sustainable. However, deficiencies in standard database values revealed inconsistencies and a value for the embodied carbon of clay was calculated using primary data. The embodied carbon value calculated from primary data was much lower than the one initially employed and hence made the clay solution more sustainable where materials were locally available

Designing with marginal fills

Some of the most sustainable and economical benefits of using geosynthetics are found in reinforcement applications. These applications allow the use of lower quality on-site material such as fine grained soils often referred to as ‘marginal fills’. This paper identifies the state of practice and understanding of designing with these soils in applications such as embankments, slopes and retaining walls. Designers often rely on published guidance documents and the paper discusses the influence BS 8006 (2010) has on the use of ‘marginal fills’ in construction and how the need for clearer more specific guidance. The study highlights that often well compacted fine grained fills placed close to optimum moisture content generate suctions, and this results in relatively high strength interaction between the fill and geosynthetic reinforcement. In cases where a fine grained fill with high moisture content is used, geosynthetic reinforcement that provides in-plane drainage may be beneficial