Abstract: Geosynthetic-reinforced soil (GRS) abutment is a load-bearing structure in bridge engineering, and its ultimate bearing capacity has not been recognized clearly. In this study, five GRS abutment centrifuge load tests were conducted under plane strain conditions. The effects of reinforcement strength, setback, and width of bearing area on the ultimate bearing capacity and failure mode of GRS abutments were investigated. The results show that the reinforcement strength significantly impacts the ultimate bearing capacity of GRS abutments. GRS abutments using high-strength reinforcement maintained stability during the loading process. It was observed that the ultimate bearing capacity of GRS abutments with low-strength reinforcement increased with the increase of setback, but its growth trend attenuated. As the bearing area width increased, the ultimate bearing capacity decreased. Compared with test results, the current semi-empirical and semi-theoretical formulas significantly underestimate the ultimate bearing capacity of GRS abutments. The observed failure surfaces all developed from the rear edge of the bearing area, extended downward at an angle to the facing, and terminated at approximately 0.5H (H is the GRS abutment height). The setback and width of bearing area affected the form and location of the failure surfaces, as well as the rupture of the reinforcement near the facing. Existing methods cannot accurately predict the bottom endpoint location and morphology below the bearing area of the failure surface. The increase in the setback and width of bearing area caused the peak strain location of each layer reinforcement to shift towards the interior of the abutment. The reinforcement strain concentrated near the free facing side of the abutment.

Key words: geosynthetic-reinforced soil, GRS abutment, ultimate bearing capacity, centrifuge test, failure surface