Ground Improvement Of Contaminated Uncontrolled Fill Using Impact Roller Compaction

This paper presents a case study of the use of an alternative ground improvement technique to treat contaminated uncontrolled fill other than traditional “remove and replace” for major earthworks for the proposed container Import and Export (IMEX) Terminal at Moorebank, Sydney. Firstly, a brief discussion of the options considered for the ground improvement including removal and replacement and the Impact Roller Compaction (IRC) method is presented. The local geological setting and the historical form of the existing Stage 1 IMEX Terminal site will be described, with the geotechnical model and associated design engineering parameters being summarised. The key points in the development of a technical specification are presented to take account of the performance requirements, including on-site IRC trial and validation testing. The primary validation measures adopted comprise plate load testing, cone penetration test (CPT) profiling, in-situ density testing, dilatometer (DMT) testing and proof rolling after IRC treatment. Surcharging was undertaken for the remediated contaminated land areas where details of the remedial treatments were not available at the Stage 1 IMEX development stage, to ensure there would be no issues resulting from long-term settlement. At the time of writing this paper, the Stage 1 IMEX works have been completed and are operational. The monitoring results indicate the performance of the site is satisfactory.