IMPROVING PAVEMENT SUBGRADE WITH THE SQUARE IMPACT ROLLER

The square Impact Roller has been used to improve ground characteristics for many decades. Originating in South Africa, it has been manufactured and further developed in Australia for nearly 20 years. Utilising rolling dynamic compaction, the Impact Roller densifies the ground to significant depths. Case study information is presented to illustrate recent uses of the square Impact Roller for subgrade improvement on two major transport related pavement projects in Adelaide, South Australia. The alignment of a 5.5km four-lane road crosses low-lying land, largely reclaimed by uncontrolled filling over many years. During early 2003, the square Impact Roller was utilised over most areas to improve subgrade conditions, to identify soft spots, voids or undesirable matter, in order to enhance the overall performance of the final pavement. The new terminal building and apron areas at Adelaide Airport will be founded on existing fill material. The use of the square Impact Roller in the preparation of the subgrade was the subject of a trial in April 2003. Detailed geotechnical testing and settlement monitoring were undertaken. Construction commenced in November 2003. The paper discusses monitoring methods and verification testing, and recommendations are made for further research into these aspects and the development of guideline specifications. 1