The influence of surcharging on deformation of 1g models of GRS walls under seismic excitation

This paper discusses the results of experiments carried out at 1g on two model geosynthetic reinforced soil walls under dynamic excitation – one with no surcharge and the other with 3kPa surcharge applied at the surface. Models were constructed in dry sand to a medium dense state with full height rigid facing and 5 layers of flexible reinforcement. Stepped sinusoidal base-input motions applied over limited time intervals with increasing acceleration amplitude at increments of 0.1g were applied until model failure. The models were well instrumented to determine accelerations, reinforcement loads and horizontal earth pressures on the retaining wall. In addition three high speed cameras focusing on different parts of the wall were used to capture the prefailure deformation by use of particle image velocimetry software (GeoPIV). Comparisons of the results show the influence of surcharging on the deformation response. Examination of the withincycle behaviour of one test provides insights as to the progressive nature of deformation of GRS walls, from engagement of reinforcement at low amplitudes of cycling to accumulation of strain at high amplitudes.