Liquefaction perspective of soil ageing

Subsoil liquefaction during strong earthquakes is one of the major seismic threats to the human community. Over the past few decades various methodologies have been proposed to assess liquefaction vulnerability; however, recent seismic events in Japan have revealed that current assessment methods are over conservative, which results in unnecessarily higher costs in mitigation measures. To overcome this situation, this study reinterprets the dynamic behaviour of sandy subsoils subject to recent and historical ground motions from Japanese seismic events and is able to demonstrate that aged soils have a higher liquefaction resistance than suggested by current design codes. Laboratory tests were also devised and conducted to study the mechanism of soil ageing at the particle scale level. Grain dislocations were observed to take place over time while boundary stress conditions maintained constant. These dislocations erased big voids, promoted a more stable granular structure and have the potential to give rise to greater liquefaction resistance.