Design of GRS bridge abutment using river debris as backfill material

The Horizon Project CIRCUIT (2024) seeks to construct a new bridge on a local road in the municipality of Črna na Koroškem, Slovenia, replacing the existing structure over a torrential creek. The project incorporates geosynthetic-reinforced soil (GRS) with cast-in-place concrete full-height rigid facing (FHR) for the bridge abutments, providing robust scour protection. In August 2023, severe flooding caused by heavy rainfall deposited large quantities of river debris—comprising silty sand and gravel—classified as non-hazardous inert waste in the area designated for the bridge construction. To enhance sustainability, this debris has been repurposed as backfill material for the new GRS bridge abutments. This paper details the material testing and design considerations for constructing the bridge abutments under these revised conditions.