Facing contribution to seismic response of reduced-scale reinforced soil walls

The behavior of six reduced-scale reinforced soil walls under base excitation is investigated using physical shaking table tests. The models were tested to isolate the influence of facing geometry, facing mass and facing toe condition on response to simulated seismic loading. The walls were instrumented to measure facing lateral displacement, reinforcement strain, toe reaction loads and accelerations. The model walls were constructed with a structural facing and polymeric geogrid reinforcement layers and subjected to a stepped amplitude sinusoidal base input acceleration. The toe boundary condition and facing panel configuration were found to have a significant effect on model response. For example, the magnitude of the accumulated facing lateral displacement at the top of the vertical wall models and at the same base acceleration magnitude was less for vertical walls with a less massive facing panel regardless of toe boundary condition. For the same boundary condition, a wall with an inclined facing displaced less than the nominal identical vertical wall for the same base excitation level. The horizontally restrained toe in reduced-scale models attracted approximately 40% to 60% of the peak total horizontal earth load during base excitation, demonstrating that a stiff facing column plays an important role in resisting dynamic loads under simulated earthquake loading. Measured footing and reinforcement loads are compared with values predicted using current pseudo-static analysis and design methods for geosynthetic-reinforced soil walls, and the implications of differences in predicted to measured values to current North American design practice are identified.