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PRESENTATION ON
LIQUEFACTION
AND
LIQUEFACTION POTENTIAL
BY: Mahesh Raj Bhatt
ME in Structural Engineering , Kathmandu Univ...
1. LIQUEFACTION:
 What is liquefaction
 When does it occur
 Liquefaction of soil
 How it works
 Shear strength of soi...
LIQUEFACTION:
In soil mechanics term “liquefied” first used by
Allen Hazen (1918), In reference to
Failure of Calaveras D...
What is Liquefaction?
A phenomenon whereby a saturated or partially
saturated soil substantially loses strength and
stiffn...
When does it occurs??
-when the effective stress of soil is reduced to
essentially zero, which corresponds to a
complete l...
Liquefaction of soil:
Soils behave like a liquid. How and why?
To understand the above phenomenon:
• some basics require...
How It Works??
• When the seismic waves pass through the soil, the
vibrations cause the individual grains in the soil to
–...
Soil loose its strength because of loss of effective
stress
Saturated sand in ground vibration,
-it tends to compact and...
How pore pressure increase
Spring water analogy of soil layer
Shear strength of soil
 Shear strength, τ = c + σt tanø
Effective stress gives more realistic behaviour of
soil, Shear s...
Influence of soil condition on liquefaction potential
Liquefaction damage 1964 Niigata japan
Alaska Earthquake (1964)
Types of liquefaction:
1. Flow liquefaction 2. Cyclic Liquefaction:
 τ static> τliquid state τ static< τliquid state
-flo...
Flow failure
Lateral spreading
Liquefaction potential/evaluation of
liquefaction hazards
Is the soil susceptible to liquefaction?
If so , will liquefac...
How to identify??
a. Historical Criteria
- earlier earthquake data/Maps/documents availale
b. Geological Criteria
• Satura...
Critical aspects of hazard evaluation
susceptibility initiation effects
yes no -monotonic
loading
-alteration of Ground
Mo...
LIQUEFACTION ANALYSIS
• Objective: does soil liquefy During Earthquake?
• Assumption: Soil act as rigid body
- moves horiz...
At force equilibrium:
Horizontal seismic force = Max. shear force at the base
of column (τmax)
Horizontal seismic force = ...
Conversion of irregular earthquake record to an
equivalent series of uniform stress cycle by
τav = τcyc = 0.65τmax = 0.65 ...
Represents liquefaction
resistance of soil
Data used: EQ ~ 7.5,
Line represents
dividing line
Three lines contain- 35,
15 ...
can liquefaction be predicted??
• NOT BUT
• Possible to identify areas giving detailed
information that have the potential...
How to mitigate Liquefaction:
a. Improving soil properties BY:
 Vibro-compaction
 Dynamic compaction
 Compacting grouti...
Dynamic compaction:
Compaction grouting
CONCLLUSIONS:
Liquefaction is most important earthquake
caused hazard all over the world.
Attention and researched shoul...
Bibliography:
• http://publication.hils.org.np/hilspub/index.php/IJLE/article/download
/97/48
• https://en.wikipedia.org/w...
THANK YOU !!!!
ANY QUARIES??
Liquefaction and liquefaction potential
Liquefaction and liquefaction potential
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Liquefaction and liquefaction potential

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liquefaction, its causes,mechanism and liquefaction potential mappings. Liquefaction analysis and measure of mitigation . along with susceptibility map of Kathmandu valley, Nepal and conclusion.

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Liquefaction and liquefaction potential

  1. 1. PRESENTATION ON LIQUEFACTION AND LIQUEFACTION POTENTIAL BY: Mahesh Raj Bhatt ME in Structural Engineering , Kathmandu University
  2. 2. 1. LIQUEFACTION:  What is liquefaction  When does it occur  Liquefaction of soil  How it works  Shear strength of soil  Types of liquefaction 2.LIQUEFACTION POTENTIAL  How to identify  Liquefaction analysis  Prediction  Mitigations 3. CONCLUSIONS:
  3. 3. LIQUEFACTION: In soil mechanics term “liquefied” first used by Allen Hazen (1918), In reference to Failure of Calaveras Dam in California.  Attention of engineer after -1964 Alaska Earthquake(Mw=9.2) good Friday earthquake - 1964 Niigata Earthquake( Ms=7.5) Japan -1989 loma-Prieta Earthquake and others.
  4. 4. What is Liquefaction? A phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid.
  5. 5. When does it occurs?? -when the effective stress of soil is reduced to essentially zero, which corresponds to a complete loss of shear strength May be initiated by – Monotonic Loading – Cyclic loading –Shock loadings(EQs)
  6. 6. Liquefaction of soil: Soils behave like a liquid. How and why? To understand the above phenomenon: • some basics required regarding:  Total stress, (σt) Pore water pressure (u) Effective stress (σeff ) σt= σeff + u σeff = σt- u
  7. 7. How It Works?? • When the seismic waves pass through the soil, the vibrations cause the individual grains in the soil to – move around and – re-adjust their positions • This ultimately results in a decrease in volume of the soil mass as – the grains pack more tightly together – a reduction in porosity
  8. 8. Soil loose its strength because of loss of effective stress Saturated sand in ground vibration, -it tends to compact and decrease in volume ; -if no drainage, decrease in volume results -increase in pore water pressure IF Pore water pressure=overburden pressure THAN effective stress = zero, -sand looses strength completely and develops a liquefied state.
  9. 9. How pore pressure increase
  10. 10. Spring water analogy of soil layer
  11. 11. Shear strength of soil  Shear strength, τ = c + σt tanø Effective stress gives more realistic behaviour of soil, Shear strength can be expressed as τ = c1 + (σt –u)tanø1 During the ground motion due to an earthquake, static pore pressure may by an amount udyn, then τ = c1 + (σn –u + udyn)tanø1 Let us consider a situation when u + udyn= σn, then τ = c1 In cohesion less soil, c1= 0, hence τ = 0 (sand)
  12. 12. Influence of soil condition on liquefaction potential
  13. 13. Liquefaction damage 1964 Niigata japan
  14. 14. Alaska Earthquake (1964)
  15. 15. Types of liquefaction: 1. Flow liquefaction 2. Cyclic Liquefaction:  τ static> τliquid state τ static< τliquid state -flow of soil mass -spreading of mass -slope ϴ >3 degree - slope ϴ <3 degree -steep area -level area -flow/often movement -lateral spreading - ground oscillation
  16. 16. Flow failure
  17. 17. Lateral spreading
  18. 18. Liquefaction potential/evaluation of liquefaction hazards Is the soil susceptible to liquefaction? If so , will liquefaction be triggered? If so , will damage occur? ANSWER IS  We Should evaluate potential liquefaction hazards
  19. 19. How to identify?? a. Historical Criteria - earlier earthquake data/Maps/documents availale b. Geological Criteria • Saturated soil deposits that have been created by – sedimentation in rivers and lakes (fluvial or alluvial deposits), – deposition of debris or eroded material (collegial deposits), – or deposits formed by wind action (Aeolian deposits) can be very liquefaction susceptible. c.Compositional Criteria -soil types clay/sand/silt -composition of soils
  20. 20. Critical aspects of hazard evaluation susceptibility initiation effects yes no -monotonic loading -alteration of Ground Motion -historical criteria Hazard do not exist (End) -cyclic loading -sand boiling -geological criteria -development of flow Liquefaction -settlements -Compositional criteria -state criteria -evaluation of liquefaction -instability -flow failures -deformation failures
  21. 21. LIQUEFACTION ANALYSIS • Objective: does soil liquefy During Earthquake? • Assumption: Soil act as rigid body - moves horizontal with amax exerted by EQ
  22. 22. At force equilibrium: Horizontal seismic force = Max. shear force at the base of column (τmax) Horizontal seismic force = Mass x Accl.= [(γt .z)/g]amax = σvo (amax/g) = τmax Mass = W/g = (γt .z)/g = σvo /g If effective vertical stress = σ’vo , Then (τmax / σ’vo ) = (σvo / σ’vo )(amax/g) In reality, during an earthquake, soil column does not act as a rigid body (τmax / σ’vo ) = rd (σvo / σ’vo )(amax/g) rd ~ 1- 0.012z , also depends upon the magnitude of the earthquake
  23. 23. Conversion of irregular earthquake record to an equivalent series of uniform stress cycle by τav = τcyc = 0.65τmax = 0.65 rd (σvo / σ’vo )(amax/g) To felicitate liquefaction analysis, define a dimensionless parameter CSR or SSR = τcyc / σ’vo = 0.65 rd (σvo / σ’vo )(amax/g) CSR = Cyclic stress ratio, SSR = Seismic stress ratio FS = Factor of safety against liquefaction = CRR/CSR CRR= Cyclic resistance ratio Time history of shear stress during earthquake for liquefaction analysis
  24. 24. Represents liquefaction resistance of soil Data used: EQ ~ 7.5, Line represents dividing line Three lines contain- 35, 15 or ≤ 5 % fine Data to the left of each line indicate field liquefaction Data to the right of each line indicate no liquefaction FS = CRR/CSR FS = Factor of safety against liquefaction CYCLIC RESISTANCE RATIO (CRR)
  25. 25. can liquefaction be predicted?? • NOT BUT • Possible to identify areas giving detailed information that have the potential of liquefaction • Liquefaction susceptibility: (Controlling factor: soil type, density and water) table • Liquefaction opportunity: (Frequency of earthquake occurrence, intensity of seismic ground shaking)
  26. 26. How to mitigate Liquefaction: a. Improving soil properties BY:  Vibro-compaction  Dynamic compaction  Compacting grouting  Stone columns b. Lowering ground water table: c. Ground surface correction. d. BE CAREFULL ABOUT HAZARD MAPING.
  27. 27. Dynamic compaction:
  28. 28. Compaction grouting
  29. 29. CONCLLUSIONS: Liquefaction is most important earthquake caused hazard all over the world. Attention and researched should be increased in it. Hazard mapping are compulsory in Nepal. (terai and valley regions) - pokhara valley is most susceptible in Nepal. Implementation of mapping should be kept in mind by all.
  30. 30. Bibliography: • http://publication.hils.org.np/hilspub/index.php/IJLE/article/download /97/48 • https://en.wikipedia.org/wiki/Soil_liquefaction • http://www.slideshare.net/jagadanand/liquefaction-of- soil?qid=28563337-882f-4bb0-adef- ae2c8d7707e1&v=&b=&from_search=1 • https://theses.lib.vt.edu/theses/available/etd- 219182249741411/unrestricted/Chp07.pdf • epa.ohio.gov/portals/34/document/guidance/gd_660_chapter_5.pdf • Geotechnical earthquake engineering Steven L . Kramer. Pearson 2007. • Seismic analysis of structures T. K, Datta. John Wiley & Sons (Asia) Pte Ltd, 2 Clementi Loop, 2010
  31. 31. THANK YOU !!!! ANY QUARIES??

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