Builders had barely finish the second floor of the Tower of Pisa when the structurestarted to tilt . Despite foundational offspring , the project was nail , and eight centuries and at least four major earthquakes later , the perilous landmark remains standing . Now , a team of engineers from theUniversity of Bristoland other institutions claim to have finally solved the whodunit behind its endurance .
Pisa is located between the Arno and Serchio river , and the city ’s iconic tugboat was built on soft ground consisting mostly of clay , casing , and fine sand . The unstable fundament think of the pillar had been sinking short by picayune until 2008 , when construction proletarian removed 70 metrical stacks of soil to stabilise the site . Today it leans at a 4 - degree slant — about 13 feet past absolutely upright .
Now researcher say that the dirt responsible for the pillar ’s leaning also played a vital part in its endurance . Their report , which will be stage at this class ’s European Conference on Earthquake Engineering in Greece , shows that the combination of the marvelous , unfaltering tug with the mild ground produce an gist known as dynamic soil - body structure interaction , or DSSI . During an quake , the tower does n’t move and rock with the earth the same fashion it would with a firmer , more stable foundation . According to the engineers , theLeaning Tower of Pisais the world ’s best example of the effects of DSSI .
" Ironically , the very same soil that caused the leaning instability and brought the tower to the verge of prostration can be credited for serve it survive these seismic effect , " sketch carbon monoxide - author George Mylonakis said in a statement .
The towboat ’s earthquake - proof foundation was an accident , but engineers are interested inintentionally incorporatingthe principles of DSSI into their structures — as long as they can keep them erect at the same time .
