The Western Australian (WA) road network includes more than 18,000 km of highways and main roads and over 170,000 km of secondary and local roads. With such a vast network and comparatively small population, it’s necessary to have a strong commitment to low cost construction.

Geotechnical investigation and pavement design are key to the effective performance of pavements, including roads, runways, taxiways and aprons.

There are many risks associated with pavement design, construction and maintenance. Poor pavement performance can come from materials and construction practices failing to meet design requirements over the life of the asset.

Inadequate pavement performance might include:

  • Premature pavement defects such as rutting, roughness and cracking
  • Potholes
  • Excessive edge break of the seal or edge wear of unsealed shoulders
  • Corrugation, loose material or slipperiness for unsealed roads

Build from the base up

A solid performance relies on using the right materials for your basecourse or subbase course – get this right and you’re part way to paving an asset that will withstand long term wear and tear and that’s cost effective.

Granular materials that occur naturally i.e. gravelly materials occurring in nature and produced with minimal crushing, are an important source for basecourse in the construction of flexible pavements on rural highways and local roads throughout Australia.

When correctly applied these materials have proven successful when used in lightly and moderately trafficked roads (and in some cases on heavily trafficked roads). And in recent years natural materials have also been used for runway construction in the arid Pilbara – on runways supporting medium sized aircraft (up to about 100 seats).

The use and performance of these materials is largely determined by their strength and stiffness. Conventional criteria based on classification tests are generally adequate to exclude almost all materials that might perform unsatisfactorily – however they may also exclude those materials which might perform satisfactorily.

There are a number of success stories that demonstrate the considerable cost savings made by using locally occurring natural materials for pavement construction. Nonetheless we must be mindful that high quality materials are a scarce and valuable resource, so it’s important they’re conserved and not used where lower quality materials would suffice.

The application of the right knowledge and experience to the use and management of natural resources will ensure they’re not wasted.

How Coffey can help

We have a long history providing geotechnical investigation and materials testing with regards to pavement design and construction services.

Our strong capability and experience in Western Australia is unique – we provide significant understanding of in-situ materials, construction materials and the environment in which the pavement structure operates.

A little about the paper

The above touches on the key findings and understandings in the paper ‘The use of naturally occurring materials for pavements in Western Australia.’

This technical paper provides a guide to the principles and practices used to select the right natural materials for construction of roads and regional airports.

The application of engineering judgment is a significant contributor to the ongoing use of naturally occurring materials. This paper demonstrates this, and where possible is supported by relevant tests and their significance.

The Western Australian guide to selection of natural gravels was referenced in this article. The 1989 version was updated in 2003 by a joint working group from Main Roads WA and the Australian Geomechanics Society. The current document was prepared by a working group from the WA Pavements Group, a subcommittee of the Australian Geomechanics Society.

The authors of this paper were recently awarded the Australian Geomechanics Award 2015. The award recognises authors of the best paper published in Australian Geomechanics in a calendar year.