An Experimental Study on the Effects of Enhanced Drainage for Liquefaction Mitigation in Dense Urban Environments

Shallow-founded structures on liquefiable deposits are often rendered unserviceable due to excessive settlement and rotation incurred during earthquakes. Recent research has exposed the mechanisms by which large strains occur in liquefied soils, leading to foundation’s excessive settlement and rotation. The development of these mechanisms may be retarded with appropriate mitigation. Prefabricated vertical drains (PVDs) are a popular and economical mitigation measure, which have been shown to limit permanent structural settlement and tilt. However, while the popularity of these drains continues to grow, there are concerns regarding their usage in dense urban environments. This paper compares the performance during centrifuge tests of an isolated 3-story model structure, an identical structure mitigated with a network of PVDs, and a pair of dissimilar structures separated by 3 m, with and without PVDs around the smaller structure. Results show that PVDs should be designed with great caution in dense urban environments, due to their potentially negative impact on the performance of adjacent unmitigated structures.