Drainage Reinforced Geocomposite for Marginal and Cohesive Slopes and Walls

Abstract

Most practitioners and engineers who currently design walls and slopes still prefer to work with high quality and well graded granular fill as backfill. However, as we move towards a Net Zero world, engineers can make a significant difference and act to help reduce carbon emissions within projects and therefore address climate change. We also know that the infrastructure required to get to Net Zero needs to be resilient and financeable. Thus, considering marginal fills or recycled spoil generated as part of construction activities shall become the new normal for the creation of walls and slopes. Marginal fills typically have high silt and/or clay contents which, when loaded, have the potential to generate excess pore water pressures in the structural backfill. Poor drainage in the structural fill reduces the available strength of the fill, thus reducing the bond between the fill and the geogrid reinforcement. Therefore, to use marginal fill efficiently, adequate drainage must be provided in the reinforced soil structure. By using a geocomposite that combines reinforcement and drainage into geogrid sustainable and environmentally friendly slopes and walls can be designed and constructed. Between 2015 and 2017, an innovative design methodology and approach for the construction of reinforced slopes and walls, with low-permeability fills, was successfully used in the UK. The design and construction experience gained in the UK was presented also at the 11^th International Conference on Geosynthetics, in Seoul (Brusa et al, 2018), to confirm the effectiveness of the system and to give engineers confidence in the use of marginal fills in reinforced soil systems. This paper will include the most interesting and latest case histories, including a railway and highway embankments done with such a technique.