Abstract

Observations of the performance of basement walls and retaining structures in recent earthquakes show that failures of basement or deep excavation walls in earthquakes are rare even if the structures were not designed for the actual magnitude of the earthquake loading. For instance, no significant damage or failures of retaining structures occurred in the recent Wenchuan earthquake in China (2008) and the subduction earthquakes in Chile (2010) and Japan (2011). To develop a better understanding of the distribution and magnitude of the seismic earth pressures on cantilever retaining structures, a series of centrifuge experiments were performed on model retaining and basement structures with cohesionless and cohesive backfills. This paper provides a general overview of the research program and its results. Overall, for the structures examined, i.e. wall heights in the range 20-30 ft, the centrifuge data consistently shows that the maximum dynamic earth pressure increases with depth, and can be reasonably approximated by a triangular distribution. This suggests that the resultant of the dynamic earth pressure increment acts near 0.33H above the footing as opposed to 0.5-0.6 H recommended by most current design procedures. The current data suggests that cantilever walls could resist ground accelerations up to 0.4 g if designed with an adequate factor of safety.