Consolidation

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Consolidation

• By Attila Bukholcz, Michael Tse, Tong Haibin

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• Consolidation occurs when a stress is applied
  to a soil. Therefore it decreases its volume with
  time. When the soil is saturated with water, it
  will be squeezed out due to the pressure.

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• The oedometer test is a popular method to
  determine the consolidation properties. The
  apparatus consists a vertically loaded
  one-dimensional cell.

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• The sample is placed in a metal ring, then it is
  inserted into a hydraulic cell. Previously the
  water content of the soil has been determined.

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• The specimen is covered with porous plates in the
  top and the bottom, that can allow pore water to
  escape. These plates need to be previously
  saturated with water.
• During the test the cell is filled up with water
  to ensure the saturation of the sample.

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• The oedometer is fitted with a device that
  measures the settlement of the soil specimen.
  This device is connected with a computer that
  records the time (in seconds) and the settlement
  (in digital units).

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• In the loading period the pressure is applied to
  the surface of the specimen through the porous
  disc, so that the surface always remains plane.
• Before the actual test starts, the sample needs
  to be preloaded with 10kPa (2.5kg of applied
  weight).

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• In the first stage of the loading the
  displacement was increased steadily. It reached a
  level where there was no further volume change
  occurring. This was the end of the primary
  consolidation. At this stage the stress was
  doubled and the recording of data was restarted.
• If the load remained for a longer time secondary
  consolidation would have occurred.

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Calculations

• Initial moisture content
• Initial density of the specimen

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Calculations

• Initial dry density
• Particle density of the soil

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Calculations

• Initial void ratio

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• End of presentation
• Thanks you!