Engineers Australia

The design and performance of stone columns at Kooragang Coal Terminal

Stephen Jones

Abstract

This paper describes the application of vibro-replacement stone columns to improve a weak foundation and allow substantial savings in both the project schedule and the quantity of fill material. Recent expansion of the Kooragang Coal Terminal boosted the coal exporting capacity of the Port of Newcastle to 100 million tonnes per year. Port Waratah Coal Services appointed Bechtel Australia to manage the construction of a new Stacker Berm and Coal Pad, which commenced in November 2005 and was completed in March 2007.

The Kooragang Coal Terminal site is underlain by soft estuarine sediments, which are susceptible to settlement via consolidation and creep. The completed machinery berms and coal stockpiles apply surface loadings of up to 180 kPa. The foundation treatment included the installation of about 6000 stone columns by vibro-replacement through the soft sediments to a natural sand stratum.

The performance monitoring included a large scale load trial undertaken during construction. Monitoring of settlement was undertaken throughout construction and has continued post-construction. The completed Berm and Coal Pad have now been monitored for over one year in service and the results are consistent with predictions.

This paper discusses the design of the stone columns, the test pad design, numerical modelling to predict performance and the monitoring results for both the test pad and the completed facilities.