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SOIL LIQUEFACTION
-Presentation-
SPECIAL FOUNDATIONS
Student:
LAZAR Gheorghe
Group 3409
PROJECT ADVISOR:
Assoc. Prof. Eng., Ph.D. Irina
LUNGU
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Liquefaction is a process in which the
seismic shear waves cause an increase in
the pore water pressure in a cohesionlesssoil stratum. This increase in pore pressure
reduces the effective stress confining the
soil. This reduction causes a reduction ofshear modulus of the soil, which in turn,
results in increased soil deformation.
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Key Elements of Soil Liquefaction
Engineering
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Ground failures associated to
liquefaction
1. Loss of bearing strengththe ground can liquefy and lose its ability to support structures.
Fig. 1. Niigata -
JapanThese tilted
buildings and
liquefaction in this
area are probably
the most well known
examples of
liquefaction and loss
of bearing strength
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2. Lateral spreading
- the ground can slide down very gentle slopes or toward stream banks
riding on a buried liquefied layer.
Fig.2. Lateral-spreading
induced failure of a dike in
Nantou
Fig.3. Lateral spreading and settlement of
a concrete dike
3 S d b il
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3. Sand boils
- sand-laden water can be ejected from a buried liquefied layer and erupt
at the surface to form sand volcanoes; the surrounding ground often
fractures and settles.
Fig.5. Widespread sand boiling in
Zhangbin Industrial Park
Fig.4. Large scale sand boiling in
Zhangbin Industrial Park, Zhanghua
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4. Flowfailuresearth moves down steep slope with large displacement and
much internal disruption of material.
5. Groundoscillationthe surface layer, riding on a buried liquefied layer, is
thrown back and forth by the shaking and can be severely deformed.
6. Flotation
light structures that are buried in the ground (like pipelines,sewers and nearly empty fuel tanks) can float to the surface when they are
surrounded by liquefied soil.
7 S ttl t
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7. Settlement
-when liquefied ground re-consolidates following an earthquake, the
ground surface may settle or subside as shaking decreases and the
underlying liquefied soil becomes more dense.
Tilting of a resident building in Wufeng
Settlement on a street of Nantou City
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Ground improvement and structural solutions that are available to reduce hazard from liquefaction.General Category Mitigation Methods Notes
I. Excavation and/or compactiona. Excavation and disposal of liquefiable soilsb. Excavation and recompactionc. Compaction (for new fil l)
II. In-situ ground densification
a. Compaction with vibratory probes (e.g.: Vibroflotation,
Terraprobe, etc.)b. Dynamic consolidation (Heavy tamping)c. Compaction pilesd. Deep densification by blastinge. Compaction grouting
Can be coupled with
installation of gravel columns Can also provide
reinforcement
III. Selected other types of ground
treatment
a. Permeation groutingb. Jet groutingc. Deep mixingd. Drains
o Gravel drainso Sand drainso Pre-fabricated strip drains
e. Surcharge pre-loadingf. Structural fills
Many drain installation
processes also provide in-situ
densification.
IV. Berms, dikes, sea walls, and
other edge containment
structure/systemsa. Structures and/or earth structures built to provide edge
containment and thus to prevent large lateral spreading.
V. Deep foundations a. Piles (installed by driving or vibration)b. Piers (installed by drilling or excavation)
Can also provide ground
densification
VI. Reinforced shallow foundations
a. Grade beamsb. Reinforced matc. Well-reinforced and/or post-tensioned matd. "Rigid" raft
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REFERENCES:
i. Liquefaction, Flow, and Associated Ground Failure -T. Lesl ie Youd, United States Department of theInterior
ii. Recent advances in soil liquefaction engineering: Aunified and consistent framework R.B. Seed, K .O.
Cetin, R.E.S. Moss , A .M. Kammerer, J. Wu, J . M.Pestana, M. F. Riemer, R.B . Sanc io , J.D. Bray, R.E. Kayen, and A . Faris, 26th Annual ASCE Los
Angeles Geotechnical Spring Semina,April 30,2003
iii. http://geomaps.wr.usgs.gov/sfgeo/liquefaction/ iv. Seismic Design Criteria for soil liquefaction J.M.Ferri t to, NAVAL FACILITIES ENGINEERINGSERVICE CENTER June 1997
v. Characteristics of liquefied sands during Mino-
Owari, Tohnankai and Fukui Earthquakes
HideakiKish ida
http://geomaps.wr.usgs.gov/sfgeo/liquefaction/http://geomaps.wr.usgs.gov/sfgeo/liquefaction/