How Persistent Engineers Kept the Leaning Tower of Pisa Standing
Grady HillhouseofPractical Engineeringtook a look at the history of the Leaning Tower of Pisa in Italy, noting how the 12th-century tower began leaning almost immediately. A couple of wars took place at the site, along with the passage of time, which led to an increased lean. In 1990, engineers, architects, and historians knew they had to address the lean before the tower fell over.
Over the roughly six centuries from when it was built to modern time, that iconic tilt continued to increase to a pointin 1990, when the tower was closed to the publicfor fear that it was near collapse. The Italian Government appointed a committee of engineers,architects, and experts in historical restoration to decide how to fix the structure once and forall.
The engineers were very persistent and extremely inventive, using everything within their professional arsenal to keep the tower standing by reducing that lean.
They ultimately cameup with three ideas to save the tower. Thefirst one was to pump out groundwater fromthe sand below the north side of the tower... Another idea was electroosmosis...Turns out the soil was too conductive...and all the othereffects of mixing electricity andsaturated soil made the process pretty much useless ...So, the committee was down to one last idea:under-excavation. If they couldn't get the soilbelow the tower to consolidate, they could just take some out.
Ultimately, the under-excavation idea worked well, and the groundbreaking techniques are still being used today. The intention was not to straighten the tower out perfectly, but rather not to have it lean so much that it was dangerous to the public. Maintaining the signature lean also connected the building to its long history.
Of course, theydidn't straighten it all the way. The lean isn't just a fascinating oddity; it is integral to thehistorical character of the tower. It's a big part of why we care. Tilting is in the Campanile's DNA,and in that way, the stabilization project wasjust a continuation of an 850-year-old process. Unlike the millions of photos with tourists pretending to hold the tower up, the contractors, restoration experts, and engineers actually did it (for the next few centuries, at least).
