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Construction failure of structure due to geological drawbacks pisa tower
Construction failure of
Structure due to
--- Leaning Tower of PISA
• History of Construction
• Characteristics of tower
• Initial mistakes
• Cause to the lean of tower
• History of inclination
• Stress due to lean
• Efforts to save the tower
• Located in PISA, Italy at the 'Piazza dei
• Bell tower for the Cathedral.
• Renowned all over the world for its
• Popular tourist hotspot. Building was
shut down to tourists in 1990, but has
open up because of extensive
restoration efforts by government
• Building reopened in April, 2001.
History of construction
• The construction of the Tower began in 1173 and due to two long breaks it
went on for 176 years. These breaks were most likely caused by war.
• The first break came in 1178, and by that time construction work had only
reached the 4th order of the final Tower.
• The second break was in 1278 after having reached the 7th order of the
finished Tower. Completion with the rise of the bell Tower was first achieved
in 1360 and although completion would have taken almost of the time had
it not been for the two shutdowns, these have actually proven to have been
crucial for the Tower existence .
Characteristics of tower
• Weight = 14,700 metric tones
• Ring shaped diameter = 19.6 m
• Thickness of wall =4.1 m, and 2.7 m for all
• Inclination = 5 ½ degree’s to the south.
• 32,240 blocks ("ashlars") for facing the exterior
and interior of the cylindrical wall structure.
• 15 half columns at the base.
• 180 columns for base.
• 12 columns for belfry.
• Location of tower – ground
comprised of layers of sand & clay.
• Layers ran parallel except under
the foundation of the tower, where
it formed a bow shape.
• The unstable mixture of soil
material caused the soil to
compact at a different rate,
causing the tower to sink 30-40
Causes to the lean of tower
• The unstable mixture of soil – caused the tower to sink to the south
• Soil at south side compressed faster than the north side – weight
of the tower was the main factor of tilt.
• Tilting was also due to the fluctuations of the water levels.
• This caused the tower to keep shifting, as well as rotate…later
discovered by scientists that the tower’s position shifted in relation
to the ground water level.
Stress due to lean
• It was thought that the tower would tip over due to the angle of tilt.
• However, it would Collapse due to enormous stress.
• Stones on first few floors had most stress – they had to support the weight
= 14,700 tones.
• Stones on south side had stress because of incline.
• The stress kept increasing as the inclination increased, therefore there was
danger of the tower collapsing.
• The outside of the tower is made of strong marble, but the inside is made up
of rubble, hence the walls cannot support the resulting stress.
Efforts to save the tower
- stabilization efforts
• The first modern attempt at stabilization of the tower occurred in
1935, when engineers attempted to seal the base of the tower by
drilling a network of holes into the foundation and then filling
them with a cement grout mixture.
• However, this only worsened the problem by slightly increasing the
lean. The failed stabilization did result in more cautious
approaches by future preservation teams.
• In 1990, the tower was closed to the
public and apartments and houses in the
path of the tower were vacated for
safety. This was partially spurred by the
abrupt collapse of another Italian tower
(Civic Tower of Pavia) due to masonry
degradation. City officials were
concerned that if the Tower of Pavia
could collapse simply due to masonry
degradation, then collapse of the Tower
of Pisa, with its more than 5° tilt, must
have been eminent.
• The preservation team finally took
action in 1992 when the first story
was braced with steel tendons, to
relieve the strain on the vulnerable
masonry; and in 1993 when 600
tons of lead ingots were stacked
around the base of the north side
of the tower to counterweight the
• In response, in 1995, the
team opted for 10
underground steel anchors, to
invisibly yank the tower
northwards. However, this
only served to bring the tower
closer to collapse than ever
• The anchors were to be
installed, 40 meters deep,
from tensioned cables
connected to the tower’s
• In view of Pisa’s high water-table, the team froze the underlying ground
with liquid nitrogen before any anchors were installed, to protect their
excavations from flooding.
• However, it was not taken into account that water expands when it
freezes. The groundwater pushed up beneath the tower and, once the
freezing had ceased, created gaps for further settlement of the tower.
• On the night of September 7, 1995, the tower lurched southwards by
more than it had done in the entire previous year.
• The team was summoned for an emergency meeting and the anchor
plan was immediately abandoned.
• Contractors removed soil from the north side with drilling
• The tower started to sink on the north side, therefore
reducing some of the stress that was building up on the
• Suspension cables were loosely fitted to the tower so it
could pull back the tower incase it started leaning..
• Work began in 1999 and halted in 2001
after approximately 77 tons of soil had
been removed and the tower had been
straightened by 44 centimeters, returning
to its 1838 inclination.
• While more soil could have been
removed, the soil extraction program
reduced the stress on the vulnerable first
story enough to be safe, yet also
maintained the distinctive lean of the
LEANING TOWER OF PISA-TECHNICAL INFORMATION
• Height of 55.86 m (183.27 ft) on the low (south) side
and 56.7 m (186.02 ft) on the high (north) side.
• The weight of the tower is estimated to be 16,000
• The tower currently leans at an angle of 3.97°, but
leaned at an angle of 5.5° prior to the stabilization
efforts in the late 20th to early 21st centuries.
• The construction failure is only due to the
unsettlement of soil underneath the structure.
• The amount of water content in the soil is
• Soil extraction helps the structure to stabilize
for a long time without any tilt.
• A minimum amount tilt is provided to attract
Thank u.. for the people who done research
on this and made history liveable