Positional Aspects of Geotechnical Control Systems

The frequency of natural disasters worldwide has increased over the last century, with the
Asian Pacific region experiencing the highest relative number of natural disasters (Global
Natural Disaster Assessment Report, 2021). An increase in frequency and intensity of natural
disasters is forecast as a direct effect of climate change (IPCC Climate Change Report, 2023).
To allow critical infrastructure to withstand this challenge and effectively support affected
communities, a wholistic approach is now required to be applied during the design,
construction, and maintenance of key infrastructure.
Environments where rockfall and instability of natural or cut slopes are an identified
geotechnical hazard are common within the alignment of linear transport infrastructure in
mountainous terrain. Rockfall protection systems that include ‘flexible barrier’ elements, such
as catch fences or catch attenuators, are commonly designed to reduce the risks associated
with rockfall and instability of natural or cut slopes by acting as a physical barrier capable of
minimising direct interaction between the mobilised hazard and immediately adjacent
infrastructure and its users.
Competing demands associated with geotechnical catch fence installations can impose a
consequential question upon road managers: is a marginal gain in containment associated
with probability orientated system positioning worth the associated safety risks, constructability
constraints and long-term maintenance challenges that accompany their installation? Or is
there a more holistic approach that balances geotechnical risk mitigation with broader
economic and other risk factors?
The aim of this presentation will be to demonstrate, by use of the Cunninghams Gap
Reconstruction project as a live, Queensland-based case-study, how the consideration of
multiple non-geotechnical issues should directly influence geotechnical design and
construction decisions in the pursuit of optimal project outcomes. Specifically, this presentation
seeks to highlight how the definition of a project-specific ‘acceptable catch probability’
threshold can be used to deliver best-for-project outcomes.