New research has further highlighted the impact that weather events will continue to have on the structural integrity and resilience of lightweight and transport infrastructure constructed on/in expansive soils.
Many aspects and considerations for infrastructure development have remained consistent for years. A key focus on engineering principles, cost efficiency, community and stakeholder alignment are among many essential – and obvious – concerns that need to be managed.
Environmental and climate change-related factors have, in principle, always been taken into account, but have seen rapid change in recent times.
Unforeseen and unprecedented weather events pose a serious threat to the long-term future of infrastructure delivery. While these risks are well known and have been acknowledged, many industry experts believe a much wider change is needed to cater for an issue that’s already on the sector’s doorstep.
It’s people like Bikash Devkota, PhD Candidate, UniSA STEM – University of South Australia, who are helping to provide greater certainty and knowledge around how climate change-related weather events could and are impacting structures.
Devkota became interested in the topic after noticing through the news and others’ research that La Niña events had become more intense, frequent, and longer in recent decades.
La Niña refers to a weather pattern or event that results in increased average rainfall, as well as cooler than average sea surface temperatures. So, what does this have to do with infrastructure, you might ask?
Weather conditions brought on by patterns such as La Niña can have a significant impact on infrastructure resiliency and performance. In particular, prolonged rainfall, which can play havoc on clay soils and structure foundations.
“After seeing an increase in intensity and frequency, I started to think about how we could link La Niña events into geotechnical design,” Devkota says.
“When we look further into the climate cycles associated with La Niña, it can give us different moisture movement mechanisms, along with the suction profile, which will finally affect and in some cases cause the premature failure of infrastructures due to ground movement. That’s why I was also interested in how it can impact or influence changes in the industry’s current design practices.
“Our geotechnical structures can last maybe 50, or 100 years. That’s why we need to account for this climate aspect well into the future.”
Related stories:
- One year milestone for $700M Singleton Bypass
- New Centenary Bridge now open
- Grassroots funding for road safety
Breaking it down
The research team was led by Devkota, and included Md Rajibul Karim, Md Mizanur Rahman, Hoang Bao Khoi Nguyen, and Simon Beecham.
Together, the team analysed more than 100 years of rainfall and climate data to track the impact of La Niña across Australia’s major regions.
Using a Braybrook research site in Melbourne’s west, Devkota and the research team collected data from literature and Australian Governmental websites, and used a finite element software program to simulate soil movement through what’s called a ‘SEEP/W analysis’.
“It helped us to access and understand climate data for the region across the past 27 years or so,” Devkota says. “From there, we can analyse the effect of different climate cycles within that period.”
One of the major weather patterns that arose during this period was the La Niña event that occurred at the break of the Millenium Drought (1997-2009), which caused damage to thousands of houses constructed during the drought, as soils heaved after a prolonged dry period. After conducting the analysis, the findings were clear.
“It was quite alarming,” Devkota says. “It showed that we need to take account right now, because if we are not incorporating changes into current design, into our geotechnical structures, they could potentially collapse in the future.”
Among the findings from Devkota’s research was that expansive clay soils are highly sensitive to rainfall fluctuations, making them vulnerable to swelling and shrinking during both La Niña and El Niño cycles, respectively.
He says homeowners, insurers and regulators need to consider long-term climate variability, not just short-term cycles, when assessing soil risks to building foundations. Devkota adds that there’s a greater need to update and rethink design standards and practices to incorporate local conditions and future climate cycles, perform more site-specific investigations, and avoid oversimplified assumptions in geotechnical design.
“Many industry practitioners, policy makers and other consulting authorities need to better integrate local climate and local geological factors,” he says. “What are the soil properties? What are the moisture movement patterns? They need to better account for the local climate.
“Local climate and soil condition can have a different impact if we’re using constant values of surface suction change and depth of suction change for major urban areas across Australia, as we are following in the current Australian practices, which may also not best represent local scenarios and in some cases may even magnify the ground movement, which will obviously affect the infrastructure.”
This research culminated in the publication of a paper in the Journal of Environmental Management, titled ‘The changing frequency of La Niña cycles and their effect on footing design in expansive soils’.
When it comes to the future, Devkota says there’s plenty that the industry can be doing right now.
“We need to think and act right now,” he says. “If we’re not incorporating these future projections in the current design, it’s going to be difficult to get the full functionality of geotechnical structures and potentially risk making the situation worse.”
This article was originally published in the November edition of our magazine. To read the magazine, click here.
.JPG)
.JPG)
