Built of concrete and steel, rooted in the ground and towering above it, urban infrastructure looks like the epitome of permanence. Yet these structures—highways and bridges, skyscrapers and electrical grids—are embedded in the natural world, which is changing with increasing severity and regularity. Storm winds and rain pummel exposed surfaces, earthquakes literally shake foundations, and rising sea levels threaten to inundate coastal structures.
How can we build safe, dependable infrastructure while accounting for the unpredictability of the natural world? Engineers and scientists at Arizona State University are answering these challenges with new designs, materials and knowledge aimed at making infrastructure resilient.
Unlike traditionally designed infrastructure, resilient infrastructure is designed with dynamic environments in mind. With two new multi-institutional awards, ASU is leading the charge to advance resilient infrastructure research and practices that may change the way cities are built in the future.
Looking to ants, moles and microbes
Researchers at the new ASU Center for Bio-mediated and Bio-inspired Geotechnics (CBBG) Engineering Research Center are designing new materials and developing methods to engineer durable, adaptable infrastructure that is also environmentally sustainable. They are approaching the issue through biogeotechnical engineering, an emerging field that explores how soils behave and how that behavior affects structures.
CBBG is a National Science Foundation (NSF) Engineering Research Center (ERC). The $18.5 million, five-year award is the nation’s largest investment in geotechnics to date.
ASU is one of only two universities in the U.S. to lead two NSF Engineering Research Centers, CBBG and the Quantum Energy and Sustainable Solar Technologies (QESST) ERCs.
In order to create infrastructure with optimal performance in the face of nature’s mercurial temperament, the researchers will explore solutions that nature has already devised. This includes microbes that are able to harden porous soils and tree root systems that can stabilize soils and prevent erosion.
“In billions of years of evolution, nature has come up with some very elegant solutions to the problems we want to solve,” says Edward Kavazanjian, director of CBBG. “By employing or mimicking these natural processes, we should be able to devise some of our own elegant solutions.”
Ants offer another intriguing muse.
“Ants are a hundred times more energy-efficient at tunneling than our current technology. They excavate very carefully, and their tunnels almost never collapse,” says Kavazanjian, who is also a professor in ASU’s School of Sustainable Engineering and the Built Environment. “If we could do what ants do, we could make underground mining much safer.”
CBBG draws on collaboration and expertise from across ASU, including the Ira A. Fulton Schools of Engineering, the School of Earth and Space Exploration, the School of Life Sciences and the Mary Lou Fulton Teachers College. In addition, the center partners with 16 universities around the world, more than a dozen private companies, and multiple public infrastructure systems—including the Arizona and New Mexico transportation departments, the Los Angeles Department of Water and Power and the Port of Los Angeles.
In addition to developing new nature-inspired engineering techniques, CBBG will focus on environmental protection and restoration. For example, if engineers could design a probe with sensor technology and guidance systems that allow it to dig and tunnel through soil like a mole, it would significantly improve subsurface exploration and characterization. Rosa Krajmalnik-Brown, an associate professor in the School of Sustainable Engineering and the Built Environment, will lead these efforts.
“We want to reproduce the beneficial effects that biological and biogeochemical processes can achieve, accelerate them and then employ them on larger scales,” says Kavazanjian.
Standing up to extreme weather
The idea of harnessing nature-inspired designs that work with the environment, instead of against it, is central to the work of another research team at ASU, the Urban Resilience to Extreme Weather-Related Events Sustainability Research Network (UREx SRN). The network seeks to minimize the devastating effects of extreme weather on the infrastructure that enables transit, electricity, water and other crucial urban services.
The NSF awarded ASU $12 million over five years through its Sustainability Research Networks program, which focuses on urban sustainability. The international UREx SRN network includes researchers and partner organizations across nine cities in North and South America: Portland, Oregon; Syracuse, New York; New York City; Baltimore, Maryland; Phoenix, Arizona; Miami, Florida; Hermosillo, Mexico; San Juan, Puerto Rico; and Valdivia, Chile.
The three UREx SRN co-directors each viewed our current approach to infrastructure through the lenses of their own fields. Project Director Charles Redman, an anthropologist, recognized that infrastructure does not always serve populations equally. He gives the example of retention basins, used to collect stormwater. In some neighborhoods, these are developed into parks.
“When you drive around, the retention basins that have soccer fields in them are in the better neighborhoods. Yet it rains the same in other neighborhoods,” says Redman, founding director of ASU’s School of Sustainability.
Co-director Nancy Grimm is an ecologist and professor in the School of Life Sciences. She says infrastructure that incorporates elements of the natural environment may be more effective over the long term. For example, coastal wetlands and sand dunes are types of natural infrastructure that protect urban areas from storms and flooding.
“We're interested in letting a little bit more of nature back into the city. We can actually benefit quite a lot from using some of the characteristics of natural systems and incorporating those into our designs,” she says.
Mikhail Chester, the other co-director, is an engineer and assistant professor in the School of Sustainable Engineering and the Built Environment. He had a “light bulb moment” while driving with Grimm through north Phoenix.
“Nancy said to me, ‘How do engineers use landscape design to minimize indoor heat exposure?’ I thought about it and realized that engineers don’t think about that. Landscape architects do. We realized there’s an opportunity to rethink how disciplines can come together to design infrastructure to be more resilient to extreme events,” he recalls.
From fail-safe to safe-to-fail
Taking a holistic approach, the team will evaluate the social, ecological and technical systems (SETS) related to infrastructure. This includes recognizing the values of all stakeholders, from city decision-makers to the residents who use and are affected by infrastructure. It also involves understanding a city’s natural environment and evaluating available technology. The result will be a suite of tools to help implement urban infrastructure that is tailored to its location and safe-to-fail.
“Fail-safe is built on a risk management principle. It’s all about how often does it happen, how potentially bad is it, who does it affect? Those are the parameters you work with, and you work with acceptable levels of those parameters. It leads you to build things that are bigger and heavier,” says Redman. “Safe-to-fail has to be built on less certainty but it also has to be built on restructuring the dynamics of the system, and that’s where SETS comes in. We think we need to really understand these dynamics better than people currently do.”
One example of a safe-to-fail system exists in Scottsdale, Arizona. The Indian Bend Wash Greenbelt winds through the city in a swath of green and dappled shade. Bike paths, parks and golf courses along the wash improve social well-being for residents in the area. Trees and plants provide numerous ecosystem services such as habitats for animals, cooler air temperatures, carbon capture and oxygen production.
After it rains, the wash fills with stormwater drained from the surrounding roads and neighborhoods. Because the wash is designed to be safe-to-fail, floodwaters do occasionally wash out the bike path and create a river instead of still ponds and grassy parks. But repairs are easily made.
Alternatively, the Los Angeles River channel is designed to be fail-safe. Devastating flooding of the river in the 1800s resulted in a push to tame it. In the 1930s the river was converted—through feats of engineering and hundreds of hours of manual labor—from natural and meandering to cemented and controlled.
While directing the river through a built channel has helped to control flooding, it has also removed the ecosystem services that a river typically provides. In addition, the entire system could be paralyzed if one part of the structure sustains significant damage, such as from an earthquake. As a result, the City of Los Angeles is now planning to transform parts of the river to recapture parts of the lost ecosystem.
Creating safe-to-fail infrastructure requires consideration of SETS and the current and future needs of a city. UREx SRN teams led by one engineer, one social scientist and one environmental scientist will be based in each partner city. This ensures an interdisciplinary approach that will produce a rich understanding of infrastructure needs and impacts across cities and cultures.
“There is a lot of opportunity to think about who is vulnerable to climate change and where they live in the city, to tailor redevelopment of infrastructure to protect the people who are the most vulnerable,” says Chester. “We’re going to build infrastructure to be more resilient and equitable and not just more efficient.”
Through projects such as the UREx SRN and the CBBG ERC, ASU researchers are helping us transform our understanding of and approach to infrastructure. New research from these initiatives will contribute to more resilient, equitable and sustainable cities today and well into the future.