Soil liquefaction occurs when loose, saturated sediments lose strength and behave like a liquid rather than a solid due to increased pore water pressure during periods of intensive ground shaking, such as during earthquakes. Liquefaction can cause major damage to buildings and structures. It is most common in loose, saturated, poorly drained soils like sands and gravels. The document discusses the causes and effects of liquefaction and methods for identifying liquefaction susceptibility and mitigating the risks.

1. Liquefaction
What is soil Liquefaction?

2. Group Members
Nouman Khadim Warraich
Mirza Farquleet Baig
Haider Ali Rafique

3. What Is Liquefaction
Liquefaction is the name given to
the process that converts a solid
soil mass into a liquid.

4. What is Soil 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. 0
October 17, 1989—Soil Liquefaction in the East Bay During the Earthquake

6. 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

7. When does it Occurs
 Liquefaction occurring beneath buildings and other structures
can cause major damage during earthquakes.
 Liquefaction occurs in cohesion less soils (typically those with
a higher content of larger grains such as sand sized) which
have water in the pore spaces, and are poorly drained.

8. 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

9.  The pore water which was originally in those spaces
becomes compressed.
 increase in pore water pressure).
 The pore water pressure becomes so high, that the soil
grains become almost Floats
 causing a significant drop in the shear strength

11. Damages
 Liquefied soil, like water, cannot support the weight of whatever is lying
above it – be it the surface layers of dry soil or the concrete floors of
buildings.
 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.
 It flows out onto the surface as boils, sand volcanoes and rivers of silt. In
some cases the liquefied soil flowing up a crack can erode and widen the
crack to a size big enough to accommodate a car.

13. How to Identify?
There are a number of different ways to evaluate the
liquefaction susceptibility of a soil deposit.
 Historical Criteria
 Geological Criteria
 Compositional Criteria

14. Historical Criteria
 Observations from earlier earthquakes provide a great deal of
information
 Soils that have liquefied in the past can liquefy again in future
earthquakes.
 If you are building a house and want to find out if your site is
susceptible to liquefaction, you could investigate previous
earthquakes to see if they caused liquefaction at your site.
 Information is also available in the form of maps of areas where
liquefaction has occurred in the past and/or is expected to occur in
the future

15. Geological Criteria
 The type of geologic process that created a soil deposit
has a strong influence on its liquefaction susceptibility.
 Saturated soil deposits that have been created by
 sedimentation in rivers and lakes (fluvial or alluvial deposits),
 deposition of debris or eroded material (colluvial deposits),
 or deposits formed by wind action (aeolian deposits)
can be very liquefaction susceptible.

16. Compositional Criteria
 Liquefaction susceptibility depends on the soil type.
 Clayey soil, particularly sensitive soils, may exhibit strain-softening
behavior similar to that of liquefied soil, but do
no liquefy in the same manner as sandy soils are.

17. Compositional 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.
 In a soil with many different size particles, the small particles
tend to fill in the voids between the bigger particles thereby
reducing the tendency for densification and pore water
pressure development when shaken.

18. Types of Failure
 Cyclic Mobility
 Overturning
 Sand Boiling

19. Cyclic Mobility
 Deformations due to cyclic mobility develop incrementally because of
static and dynamic stresses that exist during an earthquake.
 Lateral spreading, a common result of cyclic mobility, can occur on gently
sloping and on flat ground close to rivers and lakes.

20. Overturning
 Liquefaction can cause Overturning of large lateral loads on foundations.
Foundation must also be able to resist horizontal loads bending moments
induced and by lateral movements.
 Liquefaction Damage: 1964 Niigata, Japan

21. Sand Boiling
 A sand boil is sand and water that come out onto the ground surface
during an earthquake as a result of liquefaction at shallow depth.
 The Damage of Port Structures (at Kushiro Port)

22. After the earthquake
 After the earthquake shaking has ceased, and liquefaction effects have
diminished (which may take several hours), the permanent effects include:
 Lowering of ground levels where liquefaction and soil ejection has
occurred. Ground lowering may be sufficient to make the surface close to
or below the water table, creating ponds.
 Disruption of ground due to lateral spreading.

23. During And After Earthquake

24. Solution
 To minimize liquefaction, one successful approach id to lower into the
ground, a self digging apparatus till the desired depth is reached; then it is
set in motion vibrating the soil surrounding it. This consolidates the sediment
layer itself, and de-waters it up to the surface.
 The ground surface will naturally alter during this process, and the surface is
graded to the desired contours, filled as necessary with overburden, and
smoothed off.
 The equipment used at Pegasus Town north of Christchurch New Zealand,
originated from Bahrein, where presumably this is the technique used to
create the 'sand islands'. PAM JAMERA

25. References
 Ambraseys, N., and Sarma, S. (1969). "Liquefaction of Soils Induced by Earthquakes,"
Bulletin of the Seismological Society of America, 59(2), 651-664.
 Arulanandan, K., Yogachandran, C., Muraleetharan, K. K., Kutter, B. L., and Chang,
G. S., (1988). "Laboratory Flow Slide During Earthquake Simulation, Centrifuge 88,
Corte, J.-F., ed., Paris, Balkema, Rotterdam, April, pp. 539-544.
 Arulanandan, K. and Scott, R. F., Eds. (1993). "Verification of Numerical Procedures for
the Analysis of Soil Liquefaction Problems," Proc. of the Intl. Conference on the
Verification of Numerical Procedures for the Analysis of Soil Liquefaction
 Problems, Davis, CA, Balkema Publishers, Rotterdam, Netherlands,

26. Any Question?