LIQUEFACTION ASSESSMENT OF RECLAIMED LAND AT CENTREPORT, WELLINGTON

Observations of liquefaction-induced damage at the port of Wellington (CentrePort) provide an opportunity to evaluate the applicability of state-of-the-practice liquefaction evaluation methodologies on reclaimed land. This study focuses on the application of widely used simplified liquefaction assessment methods on the end-dumped gravelly fills and hydraulically-placed silty and sandy fills at CentrePort for the 2013 Cook Strait, 2013 Lake Grassmere, and 2016 Kaikōura earthquakes. Liquefaction assessment of the gravel reclamation poses several challenges due to its large percentage of gravel-sized particles making it difficult to obtain high-quality in situ data. The hydraulic fills at CentrePort are also of significant interest as they relate to a range of issues in the simplified engineering assessment around effects of fines and their plasticity on the liquefaction resistance. Following the 2016 Kaikōura earthquake, subsurface explorations were performed which included 121 Cone Penetration Tests (CPTs). Results of CPT-based liquefaction triggering and post-liquefaction reconsolidation settlement assessments using state-of-the-practice procedures are discussed and compared with observed liquefaction manifestation and settlements.

Rapid Improvement Technique of Shallow Base in Super-Soft Foundation

Dredged soil once was considered as the waste and abandoned, which had resulted in serious environment pollution and high costs. Since the viewpoint of “Utilize Dredged Soil Valuably” was proposed in 1980s, the dredged soil has been used as the hydraulic fills in land reclamation, which can meet the requirements of the booming land expansion. However, most of the fresh hydraulic soil is the floating or fluid mud, and has high water content but little bearing capacity, so it is difficult for the traditional treatment methods to improve the super-soft foundation. Based on the drainage and consolidation theory, the rapid improvement technique without sand cushion for the shallow base was developed and has been applied successfully in engineering practices. The applications showed that the rapid improvement technique improved the bearing capacity of super-soft foundation substantially, and compared with the traditional vacuum preloading method, this new technique is more environment-friendly and cost-saving.