Describing the Importance of Soil Conditions in Construction by taking few examples of Collapsed structures

1. 1
Soil
- Presented By
Venkatesh

2. 2
Leaning Tower of Pisa
• Example of a structure due to deformation of
soil.
• Construction began in 1173 and continued
till 2008
• Leaning from so long nearly 840 years
• Foundation began to settle unevenly on soft soil
composed of mud, sand and clay while
constructing its third
• It was leaning 0.2 degrees north of vertical,
but by the time the workers started on seventh
floor, the tower was tilting one degree south.
 The tower’s lean gained another 1.6 degrees.

3. 3
Attempts to correct
 Made the remaining floors taller on
the south side of the tower. But the weight
only made the foundation sink further.
 Added grout to the foundation masonry.
 Pouring a concrete ring around the base.
 Applied lead weights to the high side of the
foundation.
 Installed anchored cable counterweights.
 Extracting soil from underneath the north
side.

4. 4
Final Settlement
 In 2008, engineers announced that the Tower had been
stabilized enough that it had stopped moving for the first time
since construction began.
 Its lean is now only about 5.5 degrees
 Stable for at least the next 200 years.
 In 1989, a similarly constructed bell tower in Pavia,
northern Italy, collapsed suddenly.

5. 5
Soil and its properties
Coarse Grained >75 micron
Soil
Fine Grained < 75 micron
• Index Properties of Soils -Water content
- Specific Gravity
- Particle Size
• Useful to identify, Classify and to get approximate values of
strength and hydraulic properties of soil.

6. 6
Soil Compaction
• Rolling, Tamping or Vibration
• Done to achieve
 Higher Density, Shear Strength, Load
bearing capacity.
 Lower settlement of soil.
• Mainly for road and rail embankments, back filling of retaining
walls.

7. 7
Permeability & Shear Strength
 Permeability is the property of soil which allows the water to
flow through them or void spaces.
 Useful in: Design of dams and soil slopes.
Underground water flow
• Shear Strength of soil is the resistance to deformation by
continuous displacement of soil particles.

8. 8
Earth Pressure
 Lateral earth stress is used to estimate the
amount of stress soil can exert perpendicular
to gravity.
• Retaining wall is used for maintaining the
ground surfaces at different elevations on
either side of it.
• There are 3 states:
- Active state
- Passive state
- At rest

9. 9
Slope Stability
 Key factor while constructing roads in hill areas and
embankments.
 Failure of slopes occurs due to 1)gravitational forces
2)seepage forces within the soil.
 Landslides:
 Since we cannot alter gravity, alter geometry of the man-made
slope so that the gravity effects are not detrimental.
 Groundwater table changes are the most common cause of
landslides.
 Heavy rains, leaking pipes, melting of snow in warm weather,
floods, etc can cause changes in the groundwater table
 Rain water or snow melt can be directed far away from the
slopes by building drainage channels

10. 10
 Earthquakes may cause the soil to loosen and become weak,
leading to a landslide.
 Ideal solution is to design the geometry of the slope such that it
has an adequate factor of safety even for seismic cases.
 Setback distance should be maintained between the top of
slope and construction to prevent.

11. 11
Bearing Capacity
 Capacity of soil to support the loads applied to the ground.
 Power of foundation soil to hold the forces from the
superstructure without undergoing shear failure or excessive
settlement.

12. 12
Foundation
 Part of a structural system that supports and anchors the
superstructure of a building and transmits its loads directly to
the earth.
Types:
 Shallow Foundations: If depth is equal to or less than its width.
Eg: Spread footing
• Deep Foundations: IF depth is equal or greater than its width.
Eg: Pile foundations

13. 13
Building Collapse in Shanghai
Constructed Building Underground garage

14. 14
Concrete pilings were snapped Building began to tilt.
due to the uneven lateral pressures.

15. 15

16. 16
Civil Engineering Marvels
 Rotating 17,000 ton structure 15 meters, 106 degrees
 Swing bridges are essentially movable bridges that are held in
place by a vertical locating pin and a support ring, which
enables the structures to turn around horizontally.

17. 17

18. 18

19. 19
 Highway passing between fifth and seventh floor.
 It passes through as a bridge, by supports next to the building.

20. 20
Palm Islands