liquefaction ,problems and solutions

1. Liquefaction:
A MAJOR CAUSE OF
STRUCTURAL FAILURE
DURING EARTHQUAKE
Prakash Paudel
Graphic Era University

3. INTRODUCTION
What is liquefaction?
Relation with earthquakes

4. DEFINITION:
phenomen
on where
in a mass
of soil
loses a
large
percentage
of its shear
resistance
when
subjected to
monotonic,
cyclic, or
shock
loading, and
flows in a
manner
resembling
a liquid
until the
shear
stresses
acting on
the mass
are as low
as the
reduced
shear
resistance

5. Soil grains Soil at normal
water pressure
Liquefied soil

6. To understand the this phenomenon
some basics required regarding:
Total stress,
Pore water pressure
Effective stress

7. Case Total
Pressure
Pore Pressure Effective
Pressure
Figure- 1 475 150 325
Figure- 2 475 250 225
Figure-1 Figure-2
Total stress, Pore water pressure and Effective stress

8. General Ground Failure Resulting
From Soil Liquefaction:
Sand boils
Lateral
spreads
Loss of
bearing
capacity
Ground
settlement
Flow failures
of slopes
Ground
oscillation

10. Lateral spread at Budharmora ((Bhuj, 2001)

11. Loss of bearing strength
Large deformation occur within the soil allowing
the structure to settle & tip
e.g., 1964 Niigata earthquake, Japan-Most
spectacular bearing failure--Kawangishicho
apartment complex, several four story building
tipped as much as 60 degree

13. Chile earthquake 1960 : An island near Valdivia- Mag. 9.5
Large settlements and differential settlements of the
ground surface-Compaction of loose granular soil by EQ

14. Japan earthquake 1964: Niigata- Mag. 7.5
Settlement and tilting of structures-liquefaction of soil

15. Flow failure
•Most catastrophic ground failure
•Lateral displacement of large masses of soil
• Mass comprised of completely liquefied soil or blocks of intact
material riding on a layer of liquefied soil
•Flow develop in loose saturated sand or silts or relatively steep
slope (>3 degree)

18. Liquefaction Mitigation
Selection of method for site improvement will
depend on:
 Location, Area,Depth,Volume of soil
Soil types, properties
Site conditions
Anticipated Earthquake loading
 Structure type and condition
Economic and social effects of
structure
Availability of necessary materials
Availability of equipments and skills

19. Liquefaction Mitigation Techniques:
Soil Improvement Methods
 Dewatering:-
Permanent dewatering systems lower ground
water levels below liquefiable soil strata, thus
preventing liquefaction .
Because lowering of water table increases the
effective stress in the soil
This alternative also involves an ongoing cost
for operating the dewatering systems

21.  stone columns:-
Stone columns works like drains

23.  excavation of poor soil:-

24. Placement of additional fill:-

25. Densification of soil :-
Various methods of
compaction

26. Smooth Wheeled Roller Sheep foot Roller
Pneumatic Tyred Roller

27. Grid Roller
Pad Foot / Tamping Rollers

28. Dynamic
compaction
Vibro
compaction

29. Compaction
Grouting
Compaction
by pile
Driving

30. Anchored pile :-

31. Liquefaction Resistant Structures

33. Deep Foundation Aspects