Wall Failures

Failures of Retaining Walls

Under static conditions, the retaining walls are acted on by body forces that relates to the mass of the wall, the soil pressures and any other external forces that are present. A retaining wall that is design properly will achieve equilibrium of these forces without inducing shear pressure that approaches the shear pressure of the soil. However, during an earthquake, inertial forces and changes in the soils strength might violate equilibrium and as a result it might deform the retaining wall. When the deformation becomes too excessive, sliding, tilting, bending or other mechanism can occur.

• Sliding or Overturning

  • Sliding occurs when the horizontal pressures are not at equilibrium. When the lateral pressures are greater than the resistance force that the wall can provide from the base.
  • Overturning occurs when moment(torque) equilibrium is not being satisfied
  • The wall can slope down because of the instability of soil that is behind and beneath the wall  

• Flexural Failure

  • Flexural failure mechanism is when:
    • the wall ruptures, fractures, and/or bends
    • This depends on the geometry, stiffness, and strength of the wall.
    • Poor drainage can lead to flexural failure
  • To stabilize the soil, bending moments occur but if the bending exceeds flexural strength of the wall, flexural failures will occur

Cases of Retaining Wall Failures

• Castle Village Retaining Wall Collapse

  • This wall was in Manhattan, New York and it collapsed on May 12 2005

  • After an investigation, it was believed that the main cause of the collapse was due to increase of pressure that developed behind the wall due to poor water drainage
  • The poor water drainage was a problem that the wall exhibited through it whole life span
  • Due to the poor drainage system the wall has had repeated incidents of:
    • Cracks within the wall
    • Movements of the wall
    • Bulging within the wall
    • Tilting and many more incidents
• • However, there had been only two repairs that were conducted on the wall
  • One was in 1985, the wall had shifted and bulged a bit
    • A repair was done by installing anchors and bolts, however the poor water drainage was not addressed
  • Then in 2004, an engineering company tired to resolve the drainage problem by installing a drainage system on the surface of the wall
    • This however failed, but even if it worked, the pressures that were caused by the water were too great for the surface drainage system to help in any way
  • Soon after the wall collapsed

References 

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