Presentation on Geotechnical ENGINEERING topic:Soil Liquefaction

1. Presented by : Muhammad Talha
Roll num : F2017132067
Presented to : Eng. Shakir Ahmed
SOIL LIQUEFACTION
Geotechnical Engineering

2. What is liquefaction?
Liquefaction is the name given to the
process that converts a solid soil mass
into a liquid.

3. What is Soil liquefaction?
A phenomenon whereby a saturated or partially saturated soil
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

4. Soil Liquefaction in the East Bay During the Earthquake in October 17, 1989

5. Soil liquefaction!

6. Conditions that Cause Liquefaction
 Liquefaction most often occurs when two conditions are met:
saturation by groundwater
strong shaking

7. When does it occur?
 Liquefaction occurs when vibrations or water pressure within a mass of
soil cause the soil particles to lose contact with one another.
May be initiated by
i. Monotonic Loading
ii. Cyclic loading

8. Cont.
 As a result, the soil behaves like a liquid, has an inability to support
weight and can flow down very gentle slopes. This condition is usually
temporary and is most often caused by an earthquake vibrating water-
saturated fill or unconsolidated soil.

9. Criteria for evaluating Soils susceptible to
Liquefaction
I. Historical criteria
II. Composition criteria
III. Geological criteria

10. Historical criteria
 Observations from earlier earthquakes provide a great deal of
information about the liquefaction susceptibility of certain types of soils
and sites
 Soils that have liquefied in the past can liquefy again in future
earthquakes.

11. Composition criteria
 Soils composed of particles that are all about the same size are more
susceptible to liquefaction than soils with a wide range of particle sizes.
 Soil deposits with rounded particles.

12. Geological criteria
 Saturated soil deposits that have been created by sedimentation in rivers
and lakes.
 deposits formed by wind action.
 deposition of debris or eroded material.

13. Effects of liquefaction
 Loss of support to building foundations.
 The liquefied soil under that weight is forced into any cracks and
crevasses it can find, including those in the dry soil above, or the cracks
between concrete slabs.
 Settlement of the ground surface due to the loss of soil from
underground.

14. Mitigation of Liquefaction hazards
I. Avoid Liquefaction susceptible soils.
II. Build Liquefaction restraint structures.
III. Improve soils prone to Liquefaction.

15. Avoid Liquefaction susceptible soils.
 By using Historical, Geological, State and Compositional criteria,
characterise the soil condition, if the soil is susceptible to liquefaction
and therefore unsuitable for the desired structure.

16. Build Liquefaction restraint structures
 If it is necessary to construct on liquefaction susceptible soil it may be possible
to make the structure to be liquefaction resistant by designing the foundation
elements to resist the effects of liquefaction.
To achieve the ductility in a building there are various aspects to consider these
include:
 Shallow foundation aspects
 Deep foundation aspects

17. Improve soils prone to Liquefaction
 Improve soils prone to Liquefaction Soils prone to liquefaction can be
improved by improving their strength, density, and drainage
characteristics of the soil.
This can be achieved by;
 Dewatering.
 Increasing the in-situ density.
 Making provisions to reduce the time required for relieving the excess pore
water pressures generated by earthquake loading.

18. Conclusion
 It can clearly be concluded that the ill effects caused by liquefaction have
devastating damages to structures built on liquefied soils.
 Hence the various methods in which the severity of damage as a result
of liquefaction can be reduced.