Considerations for the Mitigation of Earthquake-Induced Soil Liquefaction in Urban Environments

In cities, seismic coupling between structures is known to influence ground motions, settlement patterns, and demand on superstructures. Yet the effects of interactions between soil and building clusters on structural performance are poorly understood, particularly on ground susceptible to liquefaction. Existing analytical methods cannot capture the nonlinearity and complexity of seismic interactions between adjacent buildings and softened soil, while advanced numerical tools that can capture such complexities have not been validated. Consequently, liquefaction mitigation measures designed assuming no interaction between structures may perform poorly. To evaluate the appropriateness and effectiveness of a common mitigation strategyprefabricated vertical drainsin urban environments, a series of experiments were conducted on a geotechnical centrifuge. Closely spaced, dissimilar, realistic model structures were placed on a layered liquefiable soil deposit and subjected to realistic earthquake motions. Mechanistic consequences of seismic coupling due to the use of drains around the shorter structure were evaluated. The results show that the use of drains around one structure may have drastic consequences for the performance of an adjacent unmitigated structure, even causing its collapse. Engineers and planners must consider integrated mitigation strategies in dense urban environments with the goal of improving performance in building clusters rather than individual buildings.