Climate change now also threatens the stability of buildings

The earth beneath our bustling metropolises is steadily warming up, potentially threatening the integrity of buildings, bridges, and transit systems. This is a reality that subway commuters in cities like London and New York City are all too familiar with. According to new research, the rising heat levels are causing minor shifts in the ground, a phenomenon that could have significant implications for urban infrastructure.

This groundbreaking study, focusing on Chicago's Loop district, leveraged three years of data from a series of wireless temperature sensors. Alessandro Rotta Loria, a civil engineer from Northwestern University in Illinois, spearheaded the research. He utilized a 3D computer model to simulate the effects of increasing temperatures on the subterranean environment.

Rotta Loria's simulations spanned from 1951, the year when Chicago finished its subway tunnels, to a future projection up to 2051. His findings highlighted the hidden yet potentially disruptive impact of underground urban heat islands on civil structures and infrastructure.

Heat can trigger slow shifts, compression, and even sinking as the soil dries out. Besides subway tunnels, other sources of heat include underground pipelines, power lines, building foundations, and parking lots scattered across our cities.

This phenomenon is not necessarily dangerous to human safety, but it will undoubtedly disrupt the regular functioning of foundations and civil infrastructure. Buildings may not collapse due to slow heat-induced deformation, but subtle subsurface changes of a few millimeters can stress foundations and affect the durability or performance of building materials over time.

Scientists have been aware of subterranean climate change for several decades, recording hotspots in soil and groundwater beneath cities like Amsterdam, Istanbul, Nanjing, and Berlin. However, Rotta Loria's study sheds new light on the spatial variability of this phenomenon, with more significant changes observed in densely populated areas.

Rotta Loria's research found that soil temperatures in Chicago are warming at a rate of about 0.14 °C per year. He suggests that underground climate change has likely already caused undisclosed structural damage. While reducing emissions could alleviate this issue, some cities are exploring innovative solutions like heat recycling.

Heat recycling, the process of using waste heat from transit systems to warm residential buildings and water systems, could become an increasingly critical strategy as global temperatures rise and urban areas continue to expand. 

Ultimately, Rotta Loria urges that ongoing underground climate change be mitigated to prevent unwanted impacts on urban infrastructure in the future. The study, offering critical insights into this pressing issue, was published in Communications Engineering. 

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