Liquefaction Potential

8/9/2019 Liquefaction Potential

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Liquefaction Potential Evaluation by SDMT

M. MaugeriUniversity of Catania, Italy

P. MonacoUniversity of L'Aquila, Italy

Keywords: Liquefaction, Seisic Dilatoeter !SDMT", #ori$ontal Stress %nde&, S'ear (ave )elocity

*+ST*-T: T'e seisic dilatoeter !SDMT" erits to obtain arallel indeendent evaluations of liquefaction resistance - fro t'e 'ori$ontal stress inde& K D and fro t'e s'ear wave velocity V S . T'e useof V S for evaluating - is well /nown. -orrelations - -K D 'ave also been develoed in t'e last twodecades, stiulated by t'e recogni$ed sensitivity of K D to a nuber of factors w'ic' are /nown to increaseliquefaction resistance 0 suc' as stress state1'istory, restraining, aging, ceentation, structure 0 and itscorrelation to relative density and state araeter. T'e aut'ors 'ave collected in t'e recent years, usingSDMT, a large aount of arallel easureents of K D and V S in different saturated sandy soils. 2sing suc'data an evaluation 'as been ade of t'e - -K D and - -V S correlations. *dditional verification, suorted

by ore real3life liquefaction case 'istories w'ere V S and K D are /nown, is desirable.

4 %5T6D2-T%65

T'e seisic dilatoeter !SDMT", a tool initiallyconceived for researc', is gradually entering into usein routine geotec'nical investigations, allowing t'e arallel accuulation of nuerous data.

SDMT rovides, aong ot'er easureents, two araeters t'at revious e&erience 'as indicated as bearing a significant relations'i wit' t'e

liquefaction resistance of sands. Suc' araeters aret'e 'ori$ontal stress inde& K D, w'ose use for liquefaction studies was suari$ed by Monaco etal. !7889", and t'e s'ear wave velocity V S , w'oserelations'i wit' liquefaction resistance 'as beenillustrated by several *ut'ors !obertson et al. 47,obertson ; (ride 4


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effects to detect by any et'od 0 t'an t'e enetration resistance !t'e increase in K D caused by restraining was found ≈ = to < ties t'e increase in enetration resistance q D". 6n t'e ot'er 'and,aiol/ows/i et al. !4F9 a" 'ad already observedt'at reliable redictions of liquefaction resistance of sand deosits of cole& stress3strain 'istoryrequire t'e develoent of soe new in situ device!ot'er t'an -PT or SPT", ore sensitive to t'eeffects of ast stress3strain 'istories.

( Correlation K D - &elative density

%n 5- unceented sands, t'e relative density D & can be derived fro K D according to t'e correlation byeyna ; -'aeau !44" s'own in ?ig. 7. T'iscorrelation 'as been strongly confired bydataoints

CC TEST N. 216 IN TICINO SAND

KD increase +20 %

qD increase +3 %

CC TEST N. 241 IN TICINO SAND

KD increase +39 %

qD increase +11 %

?ig. 4. esults of -- testing !restraining cycles" s'owing t'e'ig'er sensitivity of K D to restraining t'an enetrationresistance q D !aiol/ows/i ; Lo Presti 4F"

?ig. 7. -orrelation K D -D & for 5- unceented sands !eyna ;-'aeau 44", also including 6'gis'ia and Keigawadataoints obtained by Tana/a ; Tana/a !4F" on 'ig'quality fro$en sales

?ig. =. *verage correlation K D - in situ state araeter ξo !Gu788>"

added by subsequent researc', in articular byadditional K D -D & dataoints !s'aded areas in ?ig. 7"obtained by Tana/a ; Tana/a !4F" at t'e sites of 6'gis'ia and Keigawa, w'ere D & was

deterined on 'ig' quality fro$en sales. ( Correlation K D - In situ state $arameter

T'e state araeter concet is an iortant steforward fro t'e conventional relative densityconcet in c'aracteri$ing soil be'avior, cobiningt'e effects of bot' relative density and stress level ina rational way. T'e state araeter !vertical distance between t'e current state and t'e critical state line int'e usual e - ln $' lot" governs t'e tendency of a sandto increase or decrease in volue w'en s'eared,'ence it is strongly related to liquefaction resistance.

More rational et'ods for evaluating - wouldrequire t'e use of t'e state araeter !see e.g.studies by +oulanger 788= and +oulanger ; %driss788>, incororating critical state concets into t'eanalytical fraewor/ used to evaluate liquefaction otential". ecent researc' suorts viewing K Dfro DMT as an inde& reflecting t'e in situ state araeter ξo. Gu !788>" identified t'e averagecorrelation K D - ξo s'own in ?ig. = !study on four

H o r i o n ! a " S ! r e s s I n # e $ K

D

e"a!i&e Densi!' D (%)


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well3/nown reference sands". -learly relations K D -ξo as t'e one s'own by Gu !788>" stronglyencourage efforts to develo et'ods to assessliquefiability by DMT.

( *!ysi"al meaning of K D

Desite t'e cole&ity of t'e 'enoena involvedin t'e blade enetration, t'e reaction of t'e soilagainst t'e face of t'e blade could be seen as an

indicator of t'e soil relu"tan"e to a voluereduction. -learly a loose collasible soil will notstrongly contrast a volue reduction and will oosea low σ! !'ence a low K D" to t'e insertion of t'e blade. Moreover suc' relu"tan"e is deterined at t'ee&isting abient stresses increasing wit' det'!aart an alteration of t'e stress attern in t'evicinity of t'e blade". T'us, at least at an intuitivelevel, a connection is e&ectable between K D and t'estate araeter.

=.7 C&&-K D "urves

?ig. > !Monaco et al. 7889" suari$es t'e variouscorrelations develoed to estiate - fro K D,e&ressed in for of - -K D boundary curvessearating ossible BliquefactionB and BnoliquefactionB regions.

Previous - -K D curves were forulated byMarc'etti !4F7", obertson ; -aanella !4F"and eyna ; -'aeau !44" 0 t'e last oneincluding liquefaction field erforance dataoints!%erial )alley, Sout' -alifornia". -outin'o ;Mitc'ell !47", based on Loa Prieta !San

?rancisco +ay" 4F eart'qua/e liquefactiondataoints, roosed a slig't correction to t'e eyna; -'aeau !44" correlation.

0

0.1

0.2

0.3

0.4

0.*

0 2 4 6 + 10

?ig. >. -3 K D curves for evaluating liquefaction resistancefro DMT !Monaco et al. 7889"

* new tentative correlation for evaluating - fro K D, to be used according to t'e Seed ; %driss !4" lot in a relatively narrowrange, very close to t'e eyna ; -'aeau !44"curve.

* new tentative - -K D curve !bold line in ?ig.>", aro&iated by t'e equation:

- C 8.848


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6f course, t'e et'od is affected by t'e saerestrictions w'ic' aly, in general, to t'e Seed ;%driss !4 E)*L2*T%65 6? - ?6M S#E* (*)E)EL6-%TG V S

T'e use of t'e s'ear wave velocity V S as an inde& of liquefaction resistance 'as been illustrated byseveral *ut'ors !obertson et al. 47, obertson ;(ride 4


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* tentative identification of iniu values of K D for w'ic' a clean sand !natural or sandfill" is safeagainst liquefaction !M C


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%n t'e e&ale s'own in ?ig. < it s'ould be notedt'at, w'ile t'e e&istence of a s'allow desiccationcrust in t'e uer ≈ F is well 'ig'lig'ted by t'e K D rofile, t'e rofile of V S , oderately increasingwit' det', is uc' ore unifor and does notaear to reflect t'e s'allow crust at all.

* siilar be'avior 'as been observed at severalof t'e investigated sites !e.g. )enice, ?ig. F".

T'e fact t'at 6- crusts suc' as t'e one in ?ig. <!believed by far not liquefiable" are unequivocallydeicted by t'e 'ig' K Ds, but are alost unfelt byV S , suggests a lesser ability of V S to rofileliquefiability.

( &ole of t!e inter$arti"le %onding

?ig. s'ows t'at t'e -assino data !to of ?ig. " aresoe'ow anoalous, in t'at 'ig' V S coe&ist wit'

low K Ds. Many of t'e sands in t'at area are /nown to be volcanic and active in develoing interarticle bonding !o$$olana".

* ossible e&lanation could be t'e following:T'e s'ear wave travels fast in t'ose sands t'an/s tot'e interarticle bonding, t'at is reserved becauset'e strains are sall. K D, by contrast, is BlowB because it reflects a different aterial, w'ere t'einterarticle bonding 'as been at least artlydestroyed by t'e strains roduced by t'e blade enetration. 6n t'e ot'er 'and, ore3ressure buildu and liquefaction are ediu3 to 'ig'3strain 'enoena. T'us, for liquefiability evaluations, t'e K D indications could ossibly be ore relevant.

?ig.


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?ig. F. SDMT results at t'e site of )enice, %taly

.7 Com$arison of C&& $redi"ted %y V S and %y K D

%n order to evaluate t'e consistency of liquefactionresistance redicted by V S and by K D for a givensand, t'e - -V S et'od by *ndrus et al. !788>"and t'e - -K D et'od by Monaco et al. !7889", reviously described, 'ave been coared!indirectly" by constructing a relations'i betweenV S and K D ilied by t'e - -V S curve for ?- ≤9 in ?ig. 9 !assuing bot' aging correction factors K a and K a. C 4" and t'e - -K D curve in ?ig. >.+ot' curves aly to agnitude Mw C < .9eart'qua/es and clean sands. T'is -3equivalence

curve was obtained by cobining Eqns. 7 and = andt'en eliinating -.T'e advantage of studying suc' V S -K D

relations'i is t'at it rovides a coarison of t'etwo liquefaction evaluation et'ods wit'outneeding to calculate -S. #ence data fro sites nots'a/en by eart'qua/es can also be used to assess t'econsistency between t'e two et'ods. T'is otion is

articular 'elful, in view of t'e lac/ of docuented

liquefaction case 'istories including DMT data. 5ote t'at a siilar rocedure was adoted by

*ndrus ; Sto/oe !7888" for coaring - froV S vs - fro SPT. %n t'at case, 'owever, t'edatabase consisted of V S and SPT data fro varioussites w'ere liquefaction 'ad actually occurred during ast eart'qua/es.

T'e -3equivalence curve is s'own in ?ig. .*lso s'own in ?ig. , sueriosed to t'e curve, arefield V S -K D data airs obtained by SDMT at severalsandy sites. Suc' V S -K D data airs are t'e sae lotted in ?ig. , deurated fro t'e V S -K D data

airs belonging to s'allow !6-" K D crusts, w'ere itis often found K D O 48. *lso, t'e dataoints s'ownin ?ig. are liited to a a&iu det' of 49 !usual det' range for liquefaction occurrence", alsoto ta/e into account t'e liits of alicability of t'eSeed ; %driss !4


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100

1*0

200

2*0

300

3*0

0 2 4 6 10 12

nt/erp

0ologna

Cassino

Catania

iumicino

enice

3ela4ny Most

?ig. . -3equivalence curve between t'e correlations - -V S !*ndrus et al. 788>" and - -K D !Monaco et al. 7889" for

clean sands and Mw C " lots very close to t'e roosed - - K D boundary curve !scaled for Mw C


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0

0.1

0.2

0.3

0.4

0.*

0 2 4 6 10

C%:; #%#

$ort o Richmon" $:R2

$ort o :a"

0

0.1

0.2

0.3

0.4

0.*

0 100 200 300

C%:; #%# $ort o Richmon" $:R2

$ort o :a"

100

1*0

200

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300

0 2 4 6 10

C%:; #%#

$ort o Richmon" $:R2

$ort o :a based on available correlations. @iven t'at D & is/nown to 'ave a strong effect on t'e cyclic and ost3cyclic loading be'avior of a saturated sand, itaears t'at V S easureents would be t'e leastsensitive for distinguis'ing aong different tyes of be'avior. ?or t'is reason, %driss ; +oulanger !788>"conclude t'at it ay be ore aroriate to view t'eV S case 'istory database as roviding bounds t'atidentify conditions w'ere liquefaction is otentially

'ig'ly li/ely, 'ig'ly unli/ely and w'ere it isuncertain w'et'er or not liquefaction s'ould bee&ected. *s suc', t'ere is still a need for aniroved understanding of V S based correlations andan assessent of t'eir accuracy relative to SPT and-PT based correlations. %n t'e ean tie, %driss ;+oulanger !788>" recoend t'at greater weig't begiven to t'e results of SPT or -PT based

NO LIQUEFACTION

LIQUEFACTION

:M $R% 1989R%'

CRR'( cur!e)Monaco et al. 2**5+

C ' c " i c S ! r e s s % a ! i o C S %

o r

C ' c " i c % e s i s ! a n c e % a ! i o C % %

KD

KD

CRR-equivalencecuve

/S1 (s)

NO LIQUEFACTION

LIQUEFACTION

:M $R% 1989R%'

C ' c " i c S ! r e s s % a ! i o C S %

o r

C ' c " i c % e s i s ! a n c e % a ! i o

C % %

/ S 1

( 0 s )

:M $R%1989R%'

CRR#1 cur!e)n"rus et al. 2**,+


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liquefaction evaluations !for aterials wit'out large article si$es".

T'e considerations e&ressed by %driss ;+oulanger !788>" for - fro -PT1SPT vs - fro V S could be e&tended to - fro K D.*ccording to t'e K D -D & correlation by eyna ;-'aeau !44" in ?ig. 7, a c'ange in D & fro =8 to F8 would increase K D fro ≈ 4.9 to ≈ >.7, i.e. afactor of ≈ 7.F, indicating a 'ig'er sensitivity of K Dt'an V S to relative density.

Moreover, researc' 'as s'own t'at K D is oresensitive t'an V S to factors suc' as stress 'istory,aging, ceentation, structure, w'ic' greatlyincrease, for a given D &, liquefaction resistance and,incidentally, are felt considerably ore t'an by enetration resistance.

Particularly relevant to t'is oint is t'e discussion by Py/e !788=". T'e *ut'or recalled t'at Seed!4


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*-K56(LED@ME5TS

T'e aut'ors wis' to t'an/ oberto Auental -outin'ofor /indly roviding t'e Loa Prieta DMTliquefaction data reort.

Diego Marc'etti is also ac/nowledged for roviding t'e SDMT data at various sites.

E?EE5-ES

*ndrus, .D. ; Sto/oe, K.#., %%. 4.

Marc'etti, S. 4F7. Detection of liquefiable sand layers byeans of quasi3static enetration tests. *ro"0 .nd 1uro$eanSym$0 on *enetration esting , *sterda, 7, F39.

Marc'etti, S. 4VI ICS)71 , 6sa/a, >, 7=37.

Porcino, D. ; @'ionna, ).5. 7887. Liquefaction of coarsegrained sands by laboratory testing on undisturbed fro$ensales !in %talian". *ro"0 Annual )eeting Italian 7eot0

&es0 IA&7 .., 5ales.eyna, ?. ; -'aeau, .L. 44. Dilatoeter +ased

Liquefaction Potential of Sites in t'e %erial )alley. *ro"0.nd Int0 Conf0 on &e"ent Adv0 in 7eot0 1art!qua3e 1ngrg0and Soil Dyn0, St. Louis, =F93=7.

obertson, P.K. ; -aanella, .@. 4F. EstiatingLiquefaction Potential of Sands 2sing t'e ?lat PlateDilatoeter. AS) 7eote"!n0 esting 6ournal , !4", =F3>8.

obertson, P.K., (oeller, D.. ; ?inn, (.D.L. 47. Seisiccone enetration test for evaluating liquefaction otentialunder cyclic loading. Canadian 7eote"!0 6nl , 7, F39.

obertson, P.K. ; (ride, -.E. 4


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Sc'ertann, .#., +a/er, (., @uta, . ; Kessler, K. 4F.-PT1DMT Auality -ontrol of @round Modification at aPower Plant. *ro"0 In Situ '9, ASC1 S$e"0 Conf0 on BUseof In Situ ests in 7eote"!n0 1ngineeringB , )irginia Tec',+lac/sburg, *S-E @eotec'n. Secial Publ. 5o. , F934884.

Seed, #.+. 4

%nvestigations 3 * eort by t'e %SSM@E -oitteeT-4. *ro"0 Int0 Conf0 on In Situ )easurement of Soil

*ro$erties and Case istories, @ali, 934=4.Goud, T.L. ; %driss, %.M. 7884. Liquefaction esistance of

Soils: Suary eort fro t'e 4 5-EE and 4F 5-EE15S? (or/s'os on Evaluation of Liquefactionesistance of Soils. 6nl 771 *S-E, 47", 7. %n situ soil testing: fro ec'anics tointerretation. *ro"0 .nd Int0 Conf0 on Site C!ara"teri?ation

ISC-., Porto, 4, =3=F.

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Liquefaction Potential