The research presented in this paper highlights the recent developments that have taken place in deep in-situ ground improvement using the high-energy impact compaction (HEIC) technology. The results of three HEIC ground improvement trials and projects are presented. The test sites were subsequently certified by recognized geotechnical consultancies and used to support economical industrial pavements, slab on ground and high-level foundations on the HEIC improved soils. The paper briefly highlights the characteristics of the three materials in each of the case studies, which are regularly encountered on construction projects for industrial, commercial and residential developments. The results provide a clear indication of the depth of influence of the high-energy impact compaction process and the significant increases in soil strength for a natural ÒmarineÓ sand, a reclaimed sand deposit and for a variable clay fill. Results from cone penetrometer tests (CPT - AS 1289 F.15. - 1977) show significant depths of influence, which for the natural ÒmarineÓ sand and variable clay fill were recorded down to depths of 4 m and for the reclaimed sand deposit were recorded down to depths of 5 m below the surface.
The effective depths of influence for the current generation of HEICs has shifted the principle of impact compaction from being simply a compaction ÒtoolÓ, for relatively shallow in-situ fill, to a deep in-situ ground improvement ÒGeotechnical SolutionÓ. Impact compactors similarly raise and drop the impact drum/s from a height as the module travels at speed along the site surface. The compaction work executed at depth is related to the momentum of the falling mass and the impulse generated on impact. With both dynamic compaction and HEIC the capacity to apply compaction effort is normally measured in terms of potential energy (mgh) input.