While it was discovered earlier that New York City was sinking due to the weight of its buildings, a new study has revealed that Chicago is sinking as well. The latter's case, however, could be attributed to underground climate change.
Underground Climate Change
Assistant professor Alessandro Rotta Loira, who is the lead author of the study from the McCormick School of Engineering at Northwestern University, explains in a statement that underground climate change is a "silent hazard." Live Science reports that the deformation of the ground results from changes in temperature. Professor Loira adds that, at present, there are no infrastructures or civil structures that are specialized for withstanding such variations.
When heated, the clay of Chicago could contract, similar to other soils that have fine grains. As such, temperature rises underground could lead to several downtown foundations undergoing slow but continuous unwanted settlement.
Researchers Examine Effects of Underground Climate Change in Chicago
To examine how underground climate change affects infrastructure situated in urban zones, the authors installed over 150 wireless temperature sensors around the Chicago Loop, the central business district of the city. These sensors were added to building basements, subway tunnels, streets, and parking garages, NBC Chicago explains. They also buried some in Grant Park for further comparison.
Results revealed that temperature levels within the Loop were usually warmer by 10 degrees Celsius compared to those of Grant Park. They were also found to be 25 degrees higher compared to surface temperatures in other areas. Findings were published in the Communications Engineering journal.
Professor Loira made use of a 3D computer model to examine the changes of the ground since 1951, which was when the subway system in the city was launched. Simulations aligned with field records. Professor Loira further conducted simulations through 2051 to see the shifts in the ground in the decades to come.
The simulations revealed that warmer temperatures could lead to the swelling and expansion of the ground upwards by 0.5 inches. Live Science adds that a building's weight could also make the ground contract and sink by 0.3 inches.
Professor Loira explains that things are sinking quite slowly, adding that underground climate change likely accounts for the cracks and excessive foundation settlements that were previously not linked to the phenomenon.
Engineering professor David Toll, who also serves as the co-director at Durham University's Institute of Hazard, Risk, and Resilience and did not participate in the study, explains that the movements are not large enough to be concerning. Nevertheless, it is not to say that temperature variations in other cities could not have potential issues.
Amidst such issues, professor Loira notes that there are several solutions to mitigate the impacts of underground climate change. Fitting underground areas with geothermal technologies or thermal insulation, for one, could aid in boosting energy efficiency and reducing waste heat.
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