Limas Final Workshop Earthquake[1]

8/2/2019 Limas Final Workshop Earthquake[1]

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Seismic-induced liquefaction

around marine structures


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Two projects in LIMAS related to

seismic-induced liquefaction

Impact of earthquake-induced liquefactionon marine structures (with special

reference to the 1999 Kocaeli (Turkey)

earthquake) Mathematical modelling of pore-pressure

generation due to earthquakes and the

effect of the 1999 Kocaeli (Turkey)

earthquake on marine structures


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Colleagues working in these two

projects. Research Team

Niels-Erik Ottesen Hansen (LICengineering,

Denmark) Andrzej Zawicki (IBW, Poland)

Waldemar Swidzinski (IBW, Poland)

Wojciech Sulisz (IBW, Poland)

Jesper Damgaard (HR Wallingford, UK)

Turan Durgunoglu (ZETAS, Turkey) B. Mutlu Sumer (Technical University of

Denmark)


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Mechanism of liquefaction

During earthquake,

the groundexperiences strong,

cyclic accelerations,

a(t)


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Mechanism of liquefaction

During earthquake,

the groundexperiences strong,

cyclic accelerations,

a(t) Equation of motion for

a soil column implies

(in its simplest form):)a(

1)( tz

gt

t =


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Mechanism of liquefaction Cyclic acceleration translates

to cyclic shear stress in the

soil! This (shaking!) will rearrange

soil grains at the expense ofpore volume

This will, in turn, pressurize

the water in the pores, and The pore pressure, p, will

begin to build up

When p reaches theoverburden-pressure value,

the soil grains will becomeunbound and completely free,suspended in the water,and

The soil in this case begins toact like a liquid, theliquefaction process !


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Mechanism of liquefaction In the case of waves?

Panel (b) is a snap-shot Soil is compressed under

wave crest, expanded

under wave trough

This will generate a shear

deformation/shear stress

like


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Mechanism of liquefaction In the case of waves?

Panel (b) is a snap-shot Soil is compressed under

wave crest, expandedunder wave trough

This will generate a sheardeformation/shear stresslike this

The shear stress will vary

periodically as the wavecontinues

Soil will undergo cyclicshear stresses! Like in

the case of earthquakes!


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Period and intensity of shaking? Period? Panel shows

acceleration responsespectrum; Peak periodsvary over the range O(0.1s)-O(1 s)

Intensity? characterizedby PGA, not shown here,may vary from practically0 to O(0.6g)

In the Turkey earthquakethe max. recordedPGA=0.407g


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Mechanism of liquefaction The liquefaction process

is followed by a stagewhere

The suspended soilgrains in the liquefied soil

begin to settle in the waterwhile the pore pressuredissipates, thecompaction process

As a result, the surface ofthe soil will experiencelarge downwarddisplacement/settlement


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Images illustrating the impact of

liquefaction on marine structures


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Kocaeli (Turkey) Earthquake, 1999, Derince Port

Backfill liquefied and eventually settled; Quay wall damaged and crane damaged,along Berth 6


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3 years after!


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Settlement of backfill along Berth 4


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Nihonkai-chubu Earthquake, 1983, Akita Port

Settlement of backfill. Sheet-pile wall damaged; Damage due to pressures on

sheet-pile wall by liquefied backfill soil


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Kocaeli (Turkey) Earthquake, 1999, Izmit Marina

Liquefaction-induced settlement


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Kocaeli (Turkey) Earthquake, 1999

Vertical settlement of 48 cm was measured at this corner of the building. Adapazari.

Similar settlements of buildings at the water front in Bahceli-Seymen, East of Golcuk!


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Kocaeli (Turkey) Earthquake, 1999

Collapsed piers along Shell-Oil and Trans-Turk properties


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Highlights of the 1999 Turkey earthquake

Will highlight the liquefaction damage on marine

structures in the Turkey earthquake, as a casehistory!

Have given a full inventory of the damage in:

Sumer, Kaya & Hansen (2002): Impact ofliquefaction on coastal structures in the 1999

Kocaeli, Turkey Earthquake, Proceedings of the

12th ISOPE Conf., vol. II, pp. 504-511


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Almost invariably, backfill areas behind

quay walls and sheet-piled structuresfailed due to liquefaction

Quay walls and sheet-piled structures

were displaced seaward, the

displacements being in the range from

O(10 cm) to O(1 m)


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There are cases where the seabed settled

(It is not clear if these settlements are caused by liquefaction (andtherefore by the resulting consolidation) or by other processes suchas slope instability, surface rupture, etc, or a combination of thoseprocesses)

There are also cases where structuressettled (Again, it is not quite clear if these settlements (and collapses) are caused

by liquefaction or by other processes such as slope instability, surfacerupture, etc, or a combination of those processes)

Our calculations indicate, however, theseabed may have experienced liquefaction


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Apartment buildings sank in the liquefied soil ofO(10-50 cm) at some water-front areas

Rubble-mound breakwaters largely survived theearthquake, except one case where

Some damage occurred to the rubble-mound

breakwater in Karamursel Eregli FishingHarbour

The damage was mostly in the form of flatteningof the cross-section, sliding of the slope, and

intrusion of the lower mound material into theloose sand


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Two interesting observations!


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95.000-ton capacity silos inDerince Port TMO facilities

survived the earthquake (This is despite the fact that alarge reclamation area settledin front of these silos)

Likewise, 510-ton shipyard

crane in UM Shipyard alsosurvived the earthquake

(Despite the large settlementof the area adjacent to thisstructure)

These structures survivedlargely because

They are supported on pilespenetrating into the stiff soil


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What are the questions adesign engineer faces?


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Questions a design engineer faces Given the design earthquake, and given the design of

the structure, the questions a design engineer faces are:

Can the soil (in the backfill, underneath, or the seabeditself supporting the structure,) be liquefied?

If the soil is liquefiable, how extensive will the damage tothe structure be?

Is this damage acceptable? (e.g., for quay walls: Is d/H < the specified value in thecode, like 1%, 5%, or 10%? e.g. PIANC, 2001, p. 34)

(If not, resort to remediation such as compaction;permeable stone / gravel columns, or drains;cementation / solidification)

With the remediation in place, what will the damage tothe structure (if any) be? Is it within the limit of damagecriteria?


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Guidelines? A substantial amount of knowledge has accumulated

over the past 40 years, addressing to these questions

This has led to excellent treatments on the generalsubject

Seismic Design (not necessarily liquefaction design)Guidelines for Marine Structures such as, among others:

CEN (European Committee for Standardization), 1994Eurocode 8: Design Provisions for EarthquakeResistance of Structures

ASCE, 1998, Seismic Guidelines for Ports

PIANC, 2001, Seismic Design Guidelines for PortStructures

All three publications included liquefaction designguidelines for marine structures


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LIMAS publication LIMAS has made an attempt to put

together a set of guidelines forliquefaction alone

This will be in the form of a paper, to be

submitted to the LIMAS Special Issue,

planned to be published in J. ASCE

Waterway, Port, Coastal and OceanEngineering


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LIMAS publication. List of contents Seismic-induced liquefaction. General

Review of the existing codes (related to marinestructures only)

Japanese experience of earthquake-induced liquefactiondamage on marine structures

Turkish experience of earthquake-induced liquefaction

damage on marine structures (with reference to 1999earthquake)

Lateral spreading

Soil improvement

Advanced mathematical modelling, and Tsunamis and their implications for marine structures


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AuthorsNiels-Erik Ottesen Hansen

Andrzej Zawicki

Jesper DamgaardB. Mutlu Sumer

We have also authors, invited from outside LIMAS:

A. Ansal (Bosporus University, Turkey)

Z. Sen (Kyushu University, Japan)

H. Yamazaki (Port and Airport Research Institute, Japan)

Y. Yuksel (Yildiz University, Turkey)

A. R. Gunbak (STFA, Turkey)

O. Cetin (METU, Turkey)

C. Synolakis (University of Southern California, USA)A.C. Yalciner (METU, Turkey)

T. Durgunoglu (ZETAS, Turkey)


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References1. Earthquake Spectra (2001). 1999 Kocaeli,

Turkey, Earthquake Reconnaissance Report,Supplement A to Earthquake Spectra, Volume16, Earthquake Engineering ResearchInstitute.

2. PIANC (2001). Seismic Design Guidelines forPort Structures. Balkema, the Netherlands.

3. Sumer, B.M., Kaya, A. & Hansen, N.-E.O.(2002): Impact of liquefaction on coastal

structures in the 1999 Kocaeli, TurkeyEarthquake, Proceedings of the 12th ISOPEConf., vol. II, pp. 504-511.

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