Physical Model Tests of Half-Scale Geosynthetic Reinforced Soil Bridge Abutments. II: Dynamic Loading

This paper presents experimental results from shaking table tests on four half-scale geosynthetic reinforced soil (GRS) bridge abutment specimens constructed using well-graded angular backfill sand, modular facing blocks, and uniaxial geogrid reinforcement to investigate the effects of applied surcharge stress, reinforcement vertical spacing, and reinforcement tensile stiffness for dynamic loading conditions. Similitude relationships for shaking table tests in a 1g gravitational field were used to scale the specimen geometry, applied surcharge stress, soil modulus, reinforcement tensile stiffness, and characteristics of the earthquake motions. Reinforcement vertical spacing and reinforcement tensile stiffness had the most significant effects on the maximum dynamic and residual wall facing displacements and bridge seat settlements. Acceleration amplification increased with elevation in the reinforced and retained soil zones. Residual vertical and lateral soil stresses were lower than the calculated values for static loading conditions. The maximum tensile strain in each reinforcement layer occurred near the facing block connection for lower layers and under the bridge seat for higher layers. The vertical seismic joint between the bridge beam and bridge seat closed during the Northridge motion, resulting in contact force. A companion paper presents experimental results for the same GRS bridge abutment specimens under static loading conditions.