Instrumented Preload at Kooragang Island

The “Stage 3 Expansion” of the Kooragang Coal Terminal was a major industrial project which boosted the coal exporting capacity of Newcastle, making the terminal the largest coal handling facility in the world. Port Waratah Coal Services appointed Bechtel Australia in July 1999 to design and construct the expansion, which was completed early 2002.

Douglas Partners Pty Ltd provided geotechnical, environmental and earthworks testing services for design and construction purposes. The site is underlain by soft estuarine sediments, which are susceptible to settlement via consolidation and creep. The investigation included extensive use of cone penetration tests (including standard friction cone, piezocone and seismic cone) to profile the subsurface conditions and provide data for settlement estimates.

A feature of the geotechnical design was the use of a two-stage 9 metre high preload to consolidate and improve ground conditions prior ot construction of the 1.2 km long coal pad and reclaimer berm. The preload was extensively monitored and the geotechnical instrumentation included settlement monitoring plates, vibrating wire piezometers, inclinometers, earth pressure cels and one extensometer installed to the bedrock at approximately 50 metres depth.

This paper describes the geotechnical investigation, preload design, setlement predictions and the monitoring results, comparing actual to predicted performance.