A framework for assessing subgrade shrink swell potential for newly constructed pavements on expansive soils in Adelaide, South Australia

In South Australia, the Department for Infrastructure and Transport (DIT) Master Specification RD-EW-D1 Design of Earthworks for Roads requires the calculation of seasonal or long-term road surface movements to be in accordance with AS 2870: Residential slabs and footings. This approach, based primarily on the instability index, is different to the soaked CBR approach followed in many other states, and requires a degree of adaptation and interpretation in its application.

This paper provides a review of the assumptions and methodology for calculating surface movements for recent highway projects in Adelaide, South Australia. Detailed calculation procedures, including the determination of characteristic surface movement and adjustments for South Australia ground conditions, are presented alongside solutions for more sustainable design. The findings of this study offer valuable insights into pavement design considerations, highlighting potential cost savings and performance improvements compared to conventional treatments. By addressing the implications of tree root suction on subgrade movement as a contributor to pavement performance, this paper contributes to the development of more resilient and sustainable urban infrastructure. This research is essential for engineers and practitioners involved in pavement design, facilitating informed decision-making and optimal infrastructure investment.