Performance observations of geosynthetic reinforced bridge abutments

Abstract

Geosynthetic Reinforced Soil - Integrated Bridge System (GRS-IBS) is a technology which has been around for almost 40 years in the United States but is now being pushed by the FHWA due to improved performance and promised cost savings in the construction of small bridges. GRS-IBS is a mechanically stabilized earth (MSE) wall acting as the abutment with a bridge deck placed on top. The vertical spacing of the geosynthetic reinforcement in a MSE wall is much larger than in a GRS-IBS abutment. MSE walls have reinforcement vertical spacing of on average 24 inches compared to GRS-IBS bridge abutment vertical spacing of 8 inches. The GRS-IBS process starts by removing material to a depth and area of the foundation for the abutment, then backfill is placed and compacted. Once the backfill is compacted, a layer of geosynthetic reinforcement is placed along with a row of precast concrete blocks to form the faces of the abutment. This process is continued until the abutment is at the level needed for the bridge girders. Bridge girders are then placed directly on the geosynthetically reinforced backfill abutment. Once the girders are in place, the abutments are then brought up to road level and pavement can be placed for the approach.