Urban areas around the world are facing a new threat called underground climate change, according to a recent study. The study, conducted by researchers at Northwestern University, found that continuous heat diffusion from buildings and underground transportation is causing the ground to warm up at an alarming rate. This warming up of the ground is leading to deformation, including expansion and contraction, which in turn causes cracks in building foundations. The researchers measured temperatures in Chicago and found that subsurface temperatures beneath the city’s central business district were often 10 degrees warmer than those in other areas.
The study highlights that our current civil infrastructure is not designed to withstand these variations in temperature. As a result, buildings and other structures may experience long-term performance and durability issues. The researchers found that the ground can swell and expand by as much as 12 millimeters due to warmer temperatures, and it can also contract and sink by as much as 8 millimeters beneath the weight of buildings. These variations exceed what many building components and foundation systems are designed to handle without compromising their operational requirements.
The phenomenon of underground climate change is not unique to Chicago; it is widespread in densely populated urban areas worldwide. Many cities are warmer than rural areas due to the heat trapped by construction materials and released into the atmosphere. Now, scientists are focusing on the subsurface counterpart of this process, which is primarily driven by human activity. The continuous emission of heat from basements, parking garages, tunnels, and trains contributes to the heating of the ground below.
To better understand the impact of underground climate change, the researchers installed sensors across the Chicago Loop, the city’s central business district. They also placed sensors beneath Grant Park, away from buildings and underground transportation systems, for comparison. The measurements revealed that subsurface temperatures beneath the Loop were often 10 degrees warmer than those beneath Grant Park. Additionally, air temperatures in underground structures can be up to 25 degrees higher than undisturbed ground temperatures.
Alessandro Rotta Loria, an assistant professor of civil and environmental engineering at Northwestern University who led the study, emphasized the need for future planning strategies to address this issue. He suggests integrating geothermal technologies to harvest waste heat and installing thermal insulation on buildings to minimize the heat entering the ground. Rotta Loria believes that these measures can help mitigate the impact of underground climate change on infrastructure.
While this study provides valuable insights into the effects of continuous heat diffusion on the ground, it is crucial to consider different perspectives and opinions on this issue. Balancing the need for sustainable urban development with the challenges posed by underground climate change is a complex task that requires further research and collaboration between scientists, architects, and policymakers. Nonetheless, this study serves as a wake-up call to ensure that our civil infrastructure is resilient enough to withstand the changing climate conditions in urban areas.
