Post-Liquefaction Settlement Reduction Due to Vertical Reinforcement of Aggregate Piers-Paper

Paper

Pdf Summary

The study evaluates how aggregate piers reduce post-liquefaction settlement through vertical (axial) reinforcement, an effect often omitted when engineers use conventional free-field settlement methods. The authors further validate the Gingery (2019) constitutive model, which simulates soil reconsolidation and stress transfer between liquefied soil and aggregate piers.<br /><br />The model was applied to blast-induced liquefaction field tests in Ferrara, Italy. Three cases were compared: untreated ground; aggregate piers with observed densification and drainage effects; and aggregate piers modeled to isolate vertical reinforcement alone. Simulated settlements for the untreated and fully improved cases agreed with field observations. In the isolated case, vertical reinforcement accounted for nearly one-third of the total settlement reduction; the remainder was attributed to densification and drainage.<br /><br />Additional simulations examined two other soil profiles, using piers with a 5% area replacement ratio and excluding densification and drainage. Vertical reinforcement reduced predicted settlements by 18–26% compared with free-field values. The amount of reduction varied with soil stratigraphy and may also depend on liquefiable-layer thickness, pier dimensions and stiffness, and treatment depth.<br /><br />The findings indicate that aggregate piers can limit post-liquefaction settlement by carrying part of the vertical load as surrounding soil reconsolidates. Because this benefit varies by site, the authors recommend site-specific numerical analyses before accounting for axial reinforcement in design.

Keywords

aggregate piers

post-liquefaction settlement

vertical reinforcement

axial reinforcement

soil reconsolidation

stress transfer

Gingery 2019 model

blast-induced liquefaction

Ferrara Italy

site-specific numerical analysis