The Leaning Tower of Pisa

1
The Leaning Tower of Pisa
Gareth Jones And Ben Fenton
2
History of Construction

• 1173 1178
• Tower completed to the 4th storey
• 1272 - 1278
• Tower completed to the 7th storey
• 1360 1370
• Bell Tower completed
• 1838
• Walkway around foundations excavated

3
Geology of Pisa

• 300m of sediments over the bedrock beneath Pisa
• Layer A 10m of fairly dense river silts
• Layer B 30m of marine clay Pancone Clay
• Layer C 260m of dense sand.
• Water table 1 2m below surface

4
Tilt Stopping Solutions

• Curving Construction
• Counter Weight
• Grouting - Masonry
• Grouting - Foundations
• Tying Masonry
• Destructive or detrimental to appearance
• Therefore temporary solutions

5
Failed Attempts

• 1995 - Anchor north side to stronger sand beneath
  clay
• Concrete ring around foundations below water
  table
• Excavation in 1838 caused inrush of water
• 1995 injected liquid nitrogen to freeze
  groundwater
• Compressed clay on south side causing greater
  tilt

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Permanent Solution

• Stabilised with 2 steel cables
• Extracted soil from North of Tower

7
Permanent Solution
8
Results
Rotation towards North
South Face Rising
North Face Sinking
9
The Future

• Scenario 1
• Tower remains stable for a period, then rotates
  southwards at a reduced rate (300 years until
  intervention).
• Scenario 2
• Rotation of the Tower will cease.

10
Thank-you
The End