presentation 2007 lazar gheorghe 3409

8/13/2019 Presentation 2007 Lazar Gheorghe 3409

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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

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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.

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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/

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