Container Terminal Development on Soft-Ground Sites: Geotechnical Considerations

Since most of the best waterfront property in port cities has already been developed, new container terminals are frequently located on sites with very poor natural soils or on reclaimed land, which typically involves very poor soils as well. The existing grade generally needs to be raised and the combination of new fill and terminal loads may result in very large settlements (i.e., > 1m or 3 ft). Such sites offer numerous geotechnical engineering challenges. Based on experiences with container terminal design on soft-ground sites in the USA (VA, SC, GA, AL, and TX) and Mexico, an overview of the necessary geotechnical considerations is presented. The planning and implementation of a site characterization program is addressed, including the consideration of in situ testing and sampling methods and the trade-off of exploration economy versus detailed strata delineation. Ground improvement by means of surcharging with prefabricated vertical drains (PVDs) is nearly always the most economical improvement method but the program details are totally dependent on the design criteria (e.g., post-construction settlement tolerance, yard loading and permissible construction time). Since settlements are large, the evaluation of the improvement options requires consideration of large-strain consolidation and the use of numerical methods. Since large quantities of fill are often required, bearing capacity, lateral squeeze, and rotational stability must be considered and some degree of staging and/or the use of geosynthetic reinforcement is often necessary. Identifying a source for the fill and developing a fill handling and placement plan may be a critical component of the overall terminal development plan. Finally, the benefits of test sections, instrumentation, and construction monitoring are presented.