Influence of prefabricated vertical drains on the seismic performance of similar neighbouring structures founded on liquefiable deposits

Increasing the resilience of structures to seismically induced soil liquefaction is a major objective for the earthquake engineering community. Increasingly, soil drains are being used to mitigate the liquefaction hazard. By facilitating drainage, excess pore pressures can be limited to acceptable levels, thus reducing settlement and rotation of structures founded on liquefiable soils. However, drain design is currently based on procedures developed for the free-field. Structures change the stress distribution and flow patterns in the soil, altering the occurrence of liquefaction. At present, none of the available engineering procedures considers soil–structure interaction (SSI) in the design of drains. In dense urban environments, further complications arise from interaction between neighbouring structures. To investigate the influence of pre-fabricated vertical drains (PVDs) on structure–soil–structure interaction (SSSI), a series of geotechnical centrifuge tests was conducted to compare the performance of an isolated structure, a pair of similar structures without mitigation and a pair of structures where PVDs were present around just one building. Results show that, without improved drainage, SSSI can reduce permanent rotation of structures. However, where PVDs were placed around one of a pair of structures, the consequences for permanent rotation of and inertial demand on the adjacent unmitigated superstructure were detrimental.