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Liquification

Presentation about liquefaction and its types

maryammansha
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Liquification

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  1. SOIL LIQUEFACTION Presented By: Maryam Mansha L1F21MSCE0008

  2. Contents • Introduction • Why Liquefaction is Important? • Types of Liquefaction • Effects of Liquefaction • Methods to Reduce Liquefaction • Conclusion

  3. Introduction • 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” is called Soil Liquefaction (Hazen,1918)

  4. Liquefaction Phenomena Before Liquefaction Saturated Soil After Liquefaction Shaking destabilize the soil by increasing the space between grains and soil flow like a fluid Soil grains in an unexcited, saturated soil deposit. Forces created by the interactions of the soil grains

  5. Why Liquefaction is Important? • Liquefaction is responsible for extreme property damage and loss of life due to a several variations of failure potential. • Liquefied ground is no longer stable to withstand the stresses or even its own weight, leading to a variety of potential failures. • The building structures will lean and fall; or at times even split open under the strains.

  6. Liquefaction-induced soil movements can push foundations out of place to the point where bridge spans loose support or are compressed to the point of buckling1964 Alaskan earthquake

  7. Lateral spreading caused the foundations of the Showa bridge in Nigata ,Japan to move laterally so much that the simply supported spans became unseated and collapsed

  8. Types of Liquefaction • Flow Liquefication: A process in which the static, equilibrium is damaged by static or dynamic loads in a soil deposit with low residual strength. It occurs when the static shear stresses in the soil exceed the shear strength of the liquefied soil. Shaking destabilizes soil by increasing space between grains and soil flow like a liquid.

  9. Types of Liquefaction • Cyclic Mobility: Cyclic mobility is a liquefaction process, caused by cyclic loading, takes place in soil deposits with static shear stresses lower than the soil strength. The deformation in cyclic liquefication are in lateral direction. The lateral deformations normally observed in roads, rivers & lakes.

  10. Effects of Liquefaction • Loss of bearing strength • Lateral spread • Settlement • Loss of lateral support • Loss of bearing support • Flotation of bearing supports

  11. Methods to Reduce Liquefaction • Avoid Liquefaction Susceptible Soils • Build Liquefaction Resistant Structures • Improve the Soil

  12. Liquefaction Susceptible Soils • Soils that have liquefied in the past can liquefy again in future earthquakes. • Silty soils are susceptible to liquefaction if they satisfy the criteria given below. • Fraction finer than 0.005 mm< 15% • Liquid Limit, LL < 35% •  Natural water content > 0.9 LL • Liquidity Index < 0.75

  13. Build Liquefaction Resistant Structures • A stiff foundation mat is a good type of shallow foundation, which can transfer loads from locally liquefied zones to adjacent stronger ground.

  14. Build Liquefaction Resistant Structures • It is important that all foundation elements in a shallow foundation are tied together to make the foundation move or settle uniformly, thus decreasing the amount of shear forces induced in the structural elements resting upon the foundation.

  15. Improve the Soil • Vibro Compaction Vibro-compaction (or vibro-densification) is a method for compacting deep granular soils by repeatedly inserting a vibratory probe. Benefits can be - increased bearing capacity, reduced settlement, increased shear strength, and increased resistance to liquefaction. Max. 60m PenetrationCompaction Backfill

  16. Improve the Soil • Vibro Replacement Vibro Replacement is a technique of constructing stone columns through fill material. Depth 20-40 m.

  17. Improve the Soil • Deep Soil Mixing • By varying the proportion of lime, cement and admixtures, a range of strength gains can be achieved. The greatest improvements can be achieved in inorganic soils with low moisture content. Extremely good results can also be achieved in sensitive clays. Max. 25m

  18. Improve the Soil • Compaction Grouting • Compaction grouting is a technique in which a stiff to plastic grout is injected into the soil under pressure. It expands in the soil as a relatively homogenous mass and at the same time forming almost ball-shaped grout bulbs. The soil surrounding the grouted area is displaced and at the same time compacted. Max.40 m

  19. Conclusion: The ill effect caused by liquefaction have devastating damages to structure built on liquified soils. Hence the various methods which reduce the severity of damage as a result of liquefaction must be used.

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