HARDNESS, FRACTURE TOUGHNESS AND STRENGTH OF CERAMICS
Green liquefaction arrangement
1. A MAJOR CAUSE OF STRUCTURAL
FAILURE DURING EARTHQUAKE
2. Soil liquefaction describes a phenomenon whereby
a saturated soil substantially loses strength and
stiffness in response to an applied stress usually
earth quake shaking or other sudden change in
stress condition, causing it to behave like a liquid.
3. Liquefaction is more likely to occur in loose to
moderately saturated granular soils with poor drainage
such as silty sands or sands and gravels capped or
containing seams of impermeable sediments
4. Earthquake is vibration of earth surface by waves emerging
from the source of disturbance in the earth by virtue of
release of energy in the earths crest.
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6.
7. 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
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
8. 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.
These processes sort particles into uniform grain sizes
and deposit them in loose state which tend to densify
when shaken by earthquakes
9. To understand liquefaction, it is important to recognize the
conditions that exist in a soil deposit before an earthquake. A soil
deposit consists of an assemblage of individual soil particles. If we
look closely at these particles, we can see that each particle is in
contact with a number of neighboring particles.
11. Quick sand forms when water
saturates an area of loose sand
and the ordinary sand is
agitated. When the water
trapped in the batch of sand
cannot escape, it creates
liquefied soil that can no longer
support weight. Quicksand can
be formed by standing or
(upwards) flowing underground
water (as from an underground
spring), or by earthquakes.
12. Quick clay also known as Leda
Clay in Canada, is a unique
form of highly sensitive clay,
with the tendency to change
from a relatively stiff condition
to a liquid mass when it is
disturbed. Undisturbed quick
clay resembles a water-
saturated gel. When a block of
clay is held in the hand and
struck, Quick clay behaves this
way because, although it is
solid, it has a very high water
content, up to 80%.
13. Submarine landslides are turbidity currents and
consist of water saturated sediments flowing down
slope
14. The effects of soil
liquefaction on the built
environment can be
extremely damaging.
Buildings whose foundations
bear directly on sand which
liquefies will experience a
sudden loss of support which
will result in drastic and
irregular settlement of the
building causing structural
damage.
Bridges and large buildings
constructed on pile
foundations may lose
support from the adjacent
soil and buckle or come to
rest at a tilt after shaking.
15. 1. Empirical Correlations
2. The “Simplified Procedure” by Seed and Idriss
3. Influence of Fines Content and Plasticity
4. Magnitude Correlated Duration Weighting
DWFm
5. SPT Based Triggering Correlations
16.
17. 1. Empirical Correlations : Empirical correlations
were based essentially on comparison of Grain size
distribution of the site to the grain size envelope of
sites that have liquefied in the past worldwide. This
follows the work of Nishida Fiton and others as well as
recorded liquefaction at Turnagain Heights in Alaska.
18. There are several ways in which risk and severity of
damage as a result of soil liquefaction can be reduced.
The first and most obvious is, to avoid planning
development on liquefaction susceptible soils. Besides
in-situ testing, vulnerable sites can also be identified
by researching any prior events at the site.
If it necessary to construct on liquefaction susceptible
soils, one can modify the design of a structure in
several ways to make the structure more resistant
damage potential from liquefaction
19. Methods to mitigate the effects of soil liquefaction
have been devised by earthquake engineers and
include various soil compaction techniques such as
vibro compaction
dynamic compaction
vibro stone columns
20.
21. A loose soil or
heterogeneous
granular backfill can
be compacted in
depth by the
penetration of
vibrating probes or
vibroflots. The main
purpose of Vibro
compaction, or Vibro
floatation, is to
densify the in-situ
soils by vibration.
22. The process involves of dropping a
heavy weight repeatedly on the
ground at regularly spaced intervals.
The weight and the height
determine the amount of
compaction that would occur. The
weight that is used, depends on the
degree of compaction desired and is
between 8 tons to 36 tons The
height varies from 1m to 30m.
23. Vibro replacement stone columns
are a ground improvement
technique to improve the load
bearing capacity and reduce the
settlement of the soil. On many
occasions, it is noted that the local
soil is by nature, unable to bear the
proposed structure.
Hence the use of ground
improvement techniques may be
necessitated. Use of stone columns is
one such technique. The stone
column consists of crushed coarse
aggregates of various sizes.
24. We studied soil Liquefaction in Detail with respect to
its importance, properties of soil, details of
Liquefaction, geotechnical study, evaluation
techniques and remedial measures and concluded that
liquefaction is very important phenomenon and it has
not given that much importance in India.
The detailed study of liquefaction must be
undertaken for Indian earthquake regions and the
preventive measures must be conducted in
liquefaction prone area so as to avoid the failure of
structures during earthquake. So as to be safe against
earthquake failure.
