An Easy Method of Determining Hydraulic Conductivity of Soils using Pore Pressure Response of Piezocone Penetration Test

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An Easy Method of Determining Hydraulic
Conductivity of Soils using Pore Pressure
Response of Piezocone Penetration Test

• Chung R Song, Ph.D., University of Mississippi
• Sreekar Pulijala, Graduate Assistant, University
  of Mississippi

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Overview

• Hydraulic Conductivity and Piezocone
• Hydraulic Conductivity by Piezocone Penetration
  Test
• Previous work
• Current results
• Conclusions

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Hydraulic Conductivity

• Describes the rate at which water can move
  through a permeable medium.
• Why do we need to know hydraulic conductivity of
  the soil ??
• However, the determination of hydraulic
  conductivity is time consuming and not easy.

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Piezocone

• Used for
• Site exploration
• Assessment of ground improvement
• Evaluation of contaminant transport
• Measures
• Frictional resistance
• Pore Pressure
• End bearing

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Hydraulic Conductivity by Piezocone Penetration
Test (PCPT)

• Advance Piezocone to the desired depth and hold
  it for dissipation test.
• Reliable values of Hydraulic Conductivity,
  compared to other field tests.
• This is still time consuming and expensive (half
  day).

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Pore pressure response for soil element
during PCPT
Chung R. Song and George Z. Voyiadjis (2003)
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New Method

• To overcome the drawbacks of conventional
  dissipation test and provide a more realistic
  theoretical background.
• Key idea
• Pore Pressure response of saturated soils is
  not only a function of stress-strain parameters
  but also of hydraulic conductivity.
  
• Song.C.R and
  Voyiadjis.G.Z (2003)
• Pore pressure observed by clayey soils and sandy
  soils.
• Clay High PWP
• Sand Low or Zero PWP

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Relations between the dimensionless excess PWP
during Piezocone Penetration and dimensionless
Hydraulic Conductivity
Chung R. Song and George Z. Voyiadjis (2003)
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Previous work

• Correlates the magnitude of pore water pressure
  to the Hydraulic Conductivity directly.
• Potential for real time process.
• An axi- symmetric FE program that is capable of
  simulating behavior of soils with the advancement
  of the Piezocone tip was developed and used.
• Uses the coupled theory of mixtures

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Finite Element Mesh
Chung R. Song and George Z. Voyiadjis (2003)
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Coupled equations
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Objective

• Use of Song and Voyiadjis (2003)s method (i.e.
  New method)
• To perform numerical analyses for various soil
  conditions and provide simple design charts
  (monogram type) that an engineer can use without
  great difficulties.

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Current stage

• Setting up penetration depth and number of
  increments
• By changing some material properties like
• ?, ?
• Permeability, M
• Corresponding values of PWP are obtained for each
  varying properties when others are kept constant.

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Permeability (k) vs. PWP
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M vs. PWP
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vs. PWP
?
?
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? vs. PWP
?
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Conclusions

• The trend of PWP observed by the change of
  different parameters is reasonable.
• Easy to use design charts a handy tool to
  geotechnical engineers for the determination of
  hydraulic conductivity
• Reduction in the computation time
• Can be used in seepage analysis, soil
  classification, detection of underground
  aquifers, etc

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• THANK YOU