Ground Improvement of Soft Marine Clay by Prefabricated Vertical Drains and Vacuum-Assisted Consolidation for Port Expansion in Coastal Odisha

The eastern coastline of Odisha, earmarked for major port expansion at Paradip, Dhamra, and the newly developed Gopalpur Port, overlies a thick sequence of soft marine clay deposited during Holocene sea level transgression — a geotechnical challenge that has delayed infrastructure development and increased foundation costs substantially. The marine clay at Paradip, characterised by undrained shear strength cu=20-45 kPa, liquid limit LL=62-84%, natural water content w=52-78%, and compression index Cc=0.48-0.82, is a classic normally consolidated soft clay whose high compressibility and slow drainage make conventional preloading impractically slow for the 12-18 month construction schedule of port expansion projects. This paper presents a comprehensive geotechnical investigation, ground improvement design, and instrumented monitoring study for a 14-hectare port cargo yard expansion at Paradip using a combined Prefabricated Vertical Drain (PVD) and vacuum consolidation system. Geotechnical site characterisation includes CPT soundings, vane shear, laboratory triaxial (CU and CD), oedometer, and MIP tests. PVD installation pattern (triangular, 1.2m spacing, penetrating 22m depth), drain specification (Mebra MD88), and vacuum application protocol (87 kPa applied vacuum) are designed using Barron's equal strain consolidation theory with Hansbo's modification for PVD smear effects. A 210-day instrumented monitoring programme tracking settlement, pore pressure dissipation, and lateral deformation validates the design predictions and establishes performance of the vacuum-PVD system against the design target of U=90% consolidation within 180 days.