Seismic Performance Assessment of Port Reclaimed Land Incorporating Liquefaction and Cyclic Softening

Abstract

The seismic performance of a reclaimed land part of a New Zealand Port facility was examined through Nonlinear Dynamic Analyses (NDA), under the Operating (OLE) and the Contingency Level (CLE) seismic performance levels described in ASCE/COPRI 61-14 (2014), using advanced tools to investigate the resilience of the asset under the various performance levels and evaluate the seismic hazard, investigate the failure mechanisms leading to ground deformations, and identify key factors contributing to earthquake-induced ground deformations. The geotechnical models were implemented in the finite difference software FLAC and the behaviour of the sand-like and clay-like soils was simulated using the PM4Sand and PM4Silt constitutive models, respectively. Results from the NDA suggest that a compounded effect of both liquefaction of sand-like soils and cyclic softening of clay-like soils may lead to excessive ground deformations that can have detrimental effects on this asset. Liquefaction starts to become a dominant phenomenon under the CLE NDA. Shear failures associated with ratcheting of the strains being developed within the adjacent soils are developed immediately under the revetments. This phenomenon is initiated under the OLE and becomes also dominant under the CLE performance level simulations. Although liquefaction presents a significant challenge, the seismic response of the clay-like soils is indicated to pose a much more significant problem across the site.