Shaking table tests on a cantilever retaining wall with reinforced and unreinforced backfill

Abstract

Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics (g denotes the acceleration of gravity). The model wall has a height of 1.5 m with a scale ratio of 1/4 and retains dry sand throughout. The input motions are amplified to three levels of input peak base acceleration, 0.11g, 0.24g, and 0.39g, corresponding to minor, moderate, and major earthquakes, respectively. Investigation of the seismic response of the retaining walls focuses on acceleration and lateral displacement of the wall and backfill, dynamic earth pressures, and tensile load in the reinforcements (modeled by phosphor-bronze strips welded into a mesh). The inclusion of reinforcement has been observed to improve the integrity of the wall-soil system, mitigate vibration-related damage, and reduce the fundamental frequency of a reinforced system. Propagation of acceleration from the base to the upper portion is accompanied by time delay and nonlinear amplification. A reinforced system with a lower acceleration amplification factor than the unreinforced one indicates that reinforcement can reduce the amplification effect of input motion. Under minor and moderate earthquake loadings, reinforcement allows the inertia force and seismic earth pressure to be asynchronous and decreases the seismic earth pressure when inertia forces peak. During major earthquake loading, the wall is displaced horizontally less than the backfill, with soil pushing the wall substantially; the effect of backfill reinforcement has not been fully mobilized. The dynamic earth pressure is large at the top and diminishes toward the bottom.