Shaking Table Test of a Half-Scale Geosynthetic-Reinforced Soil Bridge Abutment

Abstract

This paper presents an experimental study of the dynamic response of a half-scale geosynthetic-reinforced soil (GRS) bridge abutment system using a shaking table. Experimental design of the model specimen followed established similitude relationships for shaking table tests of reduced-scale models in a 1g gravitational field, including scaling of model geometry, geosynthetic reinforcement stiffness, backfill soil modulus, bridge load, and characteristics of the earthquake motions. The 2.7 m-high GRS bridge abutment was constructed using well-graded sand backfill, modular facing blocks, and uniaxial geogrid reinforcement with a vertical spacing of 0.15 m in both the longitudinal and transverse directions. A bridge beam was placed on the GRS bridge abutment at one end and on a concrete support wall resting on a sliding platform off the shaking table at the other end. The GRS bridge abutment system was subjected to a series of input motions in the longitudinal direction. Results indicate that the testing system performed well, and that the GRS bridge abutment experienced small deformations. For two earthquake motions, the maximum incremental residual facing displacement in model scale was 1.0 mm, and the average incremental residual bridge seat settlement in model scale was 1.4 mm, which corresponds to a vertical strain of 0.7%.

Physical Model Tests of Half-Scale Geosynthetic Reinforced Soil Bridge Abutments. I: Static Loading

“…The GRS bridge abutment specimens were constructed on the indoor uniaxial servohydraulic shaking table in the Charles Lee Powell Structural Research Laboratory at the University of California, San Diego (UCSD), which was refurbished prior to this study to increase the fidelity of dynamic motion (Trautner et al 2017). Details of the experimental design and specimen construction are provided by Zheng et al (2018c). The configuration of the GRS bridge abutment system is shown in Figure 1.…”

“…The abutment has modular block facing on three sides, including facing on the front wall (perpendicular to the bridge beam) and the two side walls (parallel to the bridge beam). The back of the abutment specimen was supported by a reaction wall consisting of a steel frame with plywood facing, which was designed to be sufficiently stiff to maintain at-rest lateral earth pressures during construction (Zheng et al 2018c).…”

“…Additional dead weights (steel plates) equal to 33 kN were evenly distributed and rigidly attached to the concrete beam to produce a total weight of 98 kN. Elastomeric bearing pads with plan dimensions of 0.45 m × 0.90 m and a thickness of 25 mm were placed under both ends of the beam (Zheng et al 2018c(Zheng et al , 2018d. For Specimens 1, 3, and 4, the total weight of the bridge beam and dead weights produced an average applied surcharge stress of 66 kPa (Table 1) on the lower GRS fill (contact area = 0.85 m 2 ).…”

“…Based on volumetric strains from the point of maximum contraction to an axial strain of 5%, the average dilation angle  = 13° (Zheng et al 2018c(Zheng et al , 2018d. A summary of soil properties is provided in Table 2.…”

“…Numerical studies also have been conducted for GRS bridge piers and abutments, and generally indicate relatively small facing displacements and bridge seat settlements (e.g., Helwany et al 2003Helwany et al , 2007Ambauen et al 2015;Leshchinsky and Xie 2015;Fox 2016, 2017;Ardah et al 2017;Rong et al 2017;Abu-Farsakh et al 2018;Zheng et al 2018aShen et al 2019). Parametric studies indicate that the relative compaction of backfill soil, reinforcement vertical spacing, reinforcement tensile stiffness, and bridge load have the most significant effects on the performance of GRS bridge abutments under static loading (Helwany et al 2007;Fox 2016, 2017).…”