2008 - NZ - Gravel Road Pavement Deterioration Models

The development of gravel deterioration models for adoption in a New Zealand gravel road management system.

Part A of this report focuses solely on the improvement of unsealed road performance through construction and maintenance processes. Reducing gravel loss can have significant benefits – not only in lowering maintenance costs, but in placing less demand on winning gravel, reducing dust emissions, less surface ravelling, better ride qualities and improved road safety. While the gravel loss model is based on existing management practices, it is important that practitioners apply latest scientific practices relating to all aspects of unsealed road management to ensure that gravel loss is minimised. The primary purpose of these notes is to provide practical guidelines on how best to handle the various factors contributing to gravel loss. Addressing some or all of these aspects will lead to a considerable reduction in gravel loss and in time the deterioration models can be calibrated to reflect the application of best practices.

Attention has to be given to a wide range of engineering practices (listed below) to ensure gravel loss is kept to a minimum:
• road geometry
• drainage
• pavement design and materials
• maintenance practices
• stabilisation practices
• performance evaluations.

The data from the past five years was analysed and the results are presented in Part B of this report. It is important to recognise the original objective of this experiment, which was to derive only a gravel loss model for application in New Zealand. Furthermore, the monitoring programme was constrained in terms of finances, which did not allow for a fullscale testing programme such as those undertaken in South Africa and Australia.