Influence of Prefabricated Vertical Drains on the Seismic Performance of Structures Founded on Liquefiable Soils

Abstract

Prefabricated vertical drains (PVDs) are commonly used to mitigate the liquefaction hazard and its consequences. However, the influence of enhanced drainage on the response and performance of soil, foundation, and structure is not well understood, hindering the development of performance-based mitigation design procedures. This paper presents results of three centrifuge experiments on 3-story and 9-story, potentially inelastic, moment-resisting structures founded on a layered liquefiable soil deposit. The paper explores the influence of PVDs on pore pressures, foundation settlement and tilt, accelerations on the foundation and structure, and deformation patterns within the beam and column fuses. Test results indicate that PVDs can be successful in reducing the extent and duration of large excess pore pressures and net foundation settlements. However, they are also generally associated with an increase in transverse acceleration and deformation demands on the foundation and superstructure. The influence of PVDs on these seismic demands and on a foundation’s permanent tilt depends strongly on the structure’s strength and dynamic properties as well as ground motion characteristics. In the case of taller, heavier, and weaker structures, this increased demand can amplify P-Δ effects, particularly when the motion resonates with building’s modal frequencies, amplifying the foundation’s permanent rotation and the structure’s flexural deflections with potentially severe consequences. These results point to the importance of considering the performance of the entire soil–foundation–structure system in an integrated manner in mitigation design.