Introduction
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Constructed between 1173 and 1372
8 storey’s high (55m)
Weighs 14,500 tons
Built on soft ground (silty/clay soil)
Inadequate Foundation lead to leaning
Several attempts made to rectify problem
Only successful attempts carried out in
(1999 and 2008)
The Construction
Built in Four Phases
Phase 1
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9 August 1173 – 1178
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Complete up to 3rd order
Subsidence becomes obvious.
1178
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WAR :
PISA v’s FIRENZE
Built in Four Phases
Phase 2
• 1185
– Fourth order completed
• 1185
– WAR : PISA v’s FIRENZE (again)
• 1198
– Tower in use – bell(s) and clock installed.
Built in Four Phases
Phase 3
• 1231 : recommencement of works.
– Under Giovanni di Simone (1260-1267) the
tower is curved.
– Reaches sixth order
• 1287
– WAR : PISA v’s GENOANS
Built in Four Phases
Phase 4
• 1319
– Seventh order built
– Tommaso di Andrea Pisano builds the bellchamber.
• 1372
– Tower complete.
Failure of Design
• 3 Reasons for the “Tower of Pisa” being
the “Leaning Tower of Pisa”
1. Soil
2. Foundation
3. Construction
1. Soil
• Built on
- marshland
- former river estuary
- water table 2m below building
- unevenly sorted layers soil
2. Foundation
• Considering weight and height ,a 3 metre
deep foundation – NOT ENOUGH
• Lucky that construction stopped for 100
years to allow soil to settle
3. Construction
• The leaning tower of Pisa is actually
curved!!!!!!!!!
• What ?
3. Construction
• To compensate for the tilt in the tower
• Higher floors were built with one side taller
than the other
• Adverse effect of changing direction of tilt
Solutions to Leaning Tower
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Excavation & Cement Injection
Lead Counterweight
Freezing & Insertion of Steel Cables
Soil Extraction
Excavation & Cement Injection
• Excavated around base
• Injection of Cement to Strengthen
Foundation.
• Result: Increase of tilt by 10%
Lead Counterweight
• 1990 - Tower Closed
Soil break-up around foundation & Structural Failure.
• 1993 – Lead Counterweight
600 tonne lead placed on North Side to reduce rotation
and Lean.
• Result: Short Term Solution
Reduced Rotation.
Stopped Lean but needed solution to reduce tilt.
Freezing & Insertion Of Steel
Cables
• 1995 – Strengthen Foundations
• Freeze Surrounding ground
• Insert Steel Cables
• Result: Increase in Tilt
• Only stopped by adding more lead to
counterweight.
• Temporary solution, not solving problem
Soil Extraction
• 1998 – All concentration on supporting
South Side.
• Soil Extraction on North Side Introduced.
210mm isolated drills extracted soil
Ground Settled – tower shifted to the north.
• Successful Result:
Reduced lean by 500mm.
Tower Stable.
Solutions
LEANING Tower Of Pisa
• Engineers could have brought Tower to
Vertical
• Wonder of Medieval World + Major source
of income to region.
• Lean remains as top is 4 metres off centre
of base.