Improving pavement subgrade with the "square" impact roller

Abstract

Paper presented at the 23rd Annual Southern African Transport Conference 12 - 15 July 2004 "Getting recognition for the importance of transport", CSIR International Convention Centre, Pretoria, South Africa. 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.