Group 10 – Disaster Project
Leaning Tower of Pisa
The most successful disaster… Ever!
Introduction
• Construction began in August 1173, originally intended to be a marble
campanile or bell tower to accompany adjacent Cathedral.
• Discrepancy about who was original architect, not actually known many
candidates.
• Widely believed design modelled on Islamic Minarets.
• Famous ‘lean’ began in 1178 upon completion of third floor, construction
stopped for almost a century at this point.
• 1272 four more floors completed, before final completion in 1372 with
addition of Bell chamber, taking 199 years from start to finish.
• 55 metres tall, weighs 14,500 tons containing 296 steps.
• 1838 circular walkway around base excavated, exacerbating lean.
• Next man to try to solve problem none other than Benito Mussolini.
• In 1990 tower closed to public for strengthening works.
• Re-opened in 2001 to the public and deemed safe for next 200 years.
Stages of Problem
1. 1178 lean ¼ deg. North
–
Soil settlement
2. South Walls extended
–
–
5th floor by 16 cm , 6th/7th floor by 3 cm
1284 Lean south by about 0.6 degree.
3. 1360 lean 1.6 deg. South
–
South wall extended by 45 cm on edifice
4. 1838 the base was dug out
–
–
–
exposing the buried foundation steps and
column plinths.
below the water table on the south side
inrush of water, which added a half degree to
the lean
What Went wrong
• Insufficient Foundations; only 2.70m deep, no
foundation piles, reason most likely high GW
level
• Poor Soil; built upon a dense clay mixture
• Bad Design; compensating by making floors
higher increased lean in the long run
• Foundation Flooding; in 1838 when base was
dug out
Solution attempts:
• Heavier Materials,
• Bend the tower;
• Counter-weight
• Steel Cables
Solution: What Finally Worked
• New Approach,
• Steel Cables,
• Soil extraction.
Despite best attempts to knock it down,
engineers finally saved the leaning
tower of Pisa!