Review of pavement construction on expansive soil in Australia

Sagun Shrestha

Expansive soils contain clay minerals that swell on wetting and shrink on drying. Pavements built on these soils suffers from shrink-swell related ground movement of the subgrade, which translates as reflective longitudinal cracking on the surfaces. Such a problem is observed in all states and territories in Australia, particularly in South Australia (SA), where it costs an average of $60/m² for repair. Austroads (2017) suggests different measures for the construction of pavement on expansive subgrades, notably using a capping layer with low permeability. CBR swell is used to characterise expansive subgrade reactivity in most road agencies in Australia. However, different minimum CBR swell limits are used by different agencies to recommend a capping layer. Also, the recommended depth of the capping layer varies between agencies, which appears to be inconsistent. The Department for Infrastructure and Transport (DIT) in SA employs AS 2870 to estimate ground movement for characterising subgrade reactivity, which is also criticized in the literature for its appropriateness in pavement construction. This paper reviews recommendations in different states and compares them for the same subgrade condition. It appeared that climatic conditions played important role in the differences observed.

About the speaker

Sagun Shrestha

Sagun Shrestha is a PhD candidate at the University of South Australia (UniSA). He graduated with his bachelor’s degree in civil engineering from Nepal in 2016. He has experience working as an engineer in the field of building construction and hydropower before coming to Australia in 2020 to pursue his master’s degree in engineering in water resources management.

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