ABSTRACT
This article describes the structural and geotechnical solutions devised to the underpinning and reinforcement of an existing gravity-type block retaining wall quay. These enhancements were essential to allow an 8-meter seabed dredging, extending from -10.00ZH to -18.00ZH, to enable the installation and operation of a high-capacity vessel synchrolift, in a region characterized by high seismic activity. In addition to the extensive dredging, the project included the construction of high-capacity complementary strengthening structures, designed to work in perfect interaction with both the soil and the existing quay infrastructure, ensuring their capacity to support the significant load increase resulting from the lifting, onshore transfer, and dry-docking operation of vessels weighing up to 9000 tonnes on reinforced concrete platform slabs, supported on bored cast-in-situ foundation piles. Focusing on the design principles, the seismic design methodologies and the sensitivity analysis procedures towards safety factor maximisation, this article spotlights key local constraints and their influence on the cost-benefit analysis process that ultimately dictated the adopted technical solutions. The article also addresses a summary of the construction sequence, highlighting the critical role of a meticulous project timeline planning. The knowledge acquired from past experience and a thorough analysis of all process variables, from conception and design to construction, proved to be indispensable to successfully achieve an unconventional underpinning and strengthening solution in a complex geotechnical environment, by means of technical systems that permitted a substantial dredging under the foundation level of an existing infrastructure, significantly enhancing its resistance in compliance with current regulations.
