Ground improvement using dynamic replacement for NCIG CET3 coal stockyard

This paper presents an overview of the geotechnical design considerations and various analytical work undertaken for the development of the 30 mega-ton per annum (Mtpa) coal stockyard area at the Coal Export Terminal 3 (CET3) on Kooragang Island, NSW. The coal stockyard of CET3 covers an area approximately 1.2 km long by 300 m wide. The site is underlain by soft compressible soil strata of variable thickness.

To support the 21m high coal stockpiles and the stacker-reclaimer machinery loads, the upper ground required stabilisation/consolidation improvement. The original design of the proposed ground improvement was to use dredged sand fill won from the proposed berth and wharf facilities constructed for the project to progressively preload the ground and eliminate the majority of the stability concerns and consolidation settlements during the construction period. However, due to programme constraints and availability of dredged sand material, ground improvement by dynamic replacement (DR) was employed to reduce construction time and need for preload material.

The project, believed to be the largest DR project completed in the Southern Hemisphere to date, was contracted to ground improvement specialist, Keller Ground Engineering on a design and construct basis, based on performance criteria to limit the post-construction settlements and satisfy the settlement criteria for machinery operation considerations.

The process of the dynamic replacement work and the construction constraints of the ground improvement technique are presented.