Reinforced soil retaining structures using geosynthetic reinforcement are accepted as standard practice by designers, contractors and clients in New Zealand and around the world. With around 50 years of experience to draw from the benefits of this technology over alternative ways of forming retaining structures are now commonly known and well documented.

The presentation will show an innovative design methodology and approach for the construction of reinforced slopes and walls, with low-permeability fills, which was successfully used in the UK and Europe.

However, most practitioners and engineers who currently design walls and slopes still prefer to work with high quality and well graded granular fill as backfill. 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 economically viable. 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. The presentation will show an innovative design methodology and approach for the construction of reinforced slopes and walls, with low-permeability fills, which was successfully used in the UK.

The talk will include also the most interesting and latest case histories, including railway and highway embankments done with such a technique.

Reinforced Slopes and Walls with Site Won and Marginal Fills - Auckland