Maugeri Monaco SOA Liquefaction 06 SDMT

8/12/2019 Maugeri Monaco SOA Liquefaction 06 SDMT

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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$ontal Stress %nde&, S'ear (ave )elocity*+ST*-T: T'e seisic dilatoeter !SDMT" erits to obtain arallel indeendent evaluations ofliquefaction resistance - fro t'e 'ori$ontal stress inde&KDand fro t'e s'ear wave velocity VS. T'e useof VS for evaluating - is well /nown. -orrelations --KD'ave also been develoed in t'e last twodecades, stiulated by t'e recogni$ed sensitivity of KDto a nuber of factors w'ic' are /nown to increaseliquefaction resistance 0 suc' as stress state1'istory, restraining, aging, ceentation, structure 0 and its

correlation 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 KDand VSin different saturated sandy soils. 2sing suc'data an evaluation 'as been ade of t'e --KDand --VScorrelations. *dditional verification, suortedby ore real3life liquefaction case 'istories w'ere VSandKDare /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'earallel accuulation of nuerous data.

SDMT rovides, aong ot'er easureents, twoaraeters t'at revious e&erience 'as indicated asbearing a significant relations'i wit' t'eliquefaction resistance of sands. Suc' araeters aret'e 'ori$ontal stress inde& KD, w'ose use forliquefaction studies was suari$ed by Monaco etal. !7889", and t'e s'ear wave velocity VS, w'oserelations'i wit' liquefaction resistance 'as beenillustrated by several *ut'ors !obertson et al. 47,obertson ; (ride 4


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by t'e eart'qua/e, g C acceleration of gravity, voand voCtotal and effective overburden stresses andrdCstress reduction coefficient deendent on det',generally in t'e range 8.F to 4.

T'e liquefaction resistance - is generallyevaluated fro in situ tests. T'e 4 5-EE and4F 5-EE15S? wor/s'os !suary reort byGoud ; %driss 7884" reviewed t'e state3of3t'e3art oft'e Seed ; %driss !4


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( Correlation KD-&elative density

%n 5- unceented sands, t'e relative densityD&canbe derived fro KDaccording 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

KDincrease +20%

qD increase +3%

CC TEST N. 241 IN TICINO SAND

KDincrease +39%

qD increase +11%

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

?ig. 7. -orrelationKD-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 correlationKD- in situ state araeter o!Gu788>"

H

orion!a"S!ressIn#e$K

D

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


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added by subsequent researc', in articular byadditionalKD -D&dataoints !s'aded areas in ?ig. 7"obtained by Tana/a ; Tana/a !4F" at t'e sites of6'gis'ia and Keigawa, w'ere D& wasdeterined on 'ig' quality fro$en sales.

( Correlation KD-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 in

a rational way. T'e state araeter !vertical distancebetween 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 liquefactionotential". ecent researc' suorts viewing KDfro DMT as an inde& reflecting t'e in situ statearaeter o. Gu !788>" identified t'e averagecorrelation KD - o s'own in ?ig. = !study on fourwell3/nown reference sands". -learly relations KD -o as t'e one s'own by Gu !788>" stronglyencourage efforts to develo et'ods to assessliquefiability by DMT.

( *!ysi"al meaning of KD

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 anindicator 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 ! !'ence a low KD" to t'e insertion of t'eblade. Moreover suc' relu"tan"e is deterined att'e e&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 betweenKDand t'estate araeter.

=.7 C&&-KD"urves

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

Previous --KD 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 liquefaction

dataoints, roosed a slig't correction to t'e eyna; -'aeau !44" correlation.


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0

0.1

0.2

0.3

0.4

0.*

0 2 4 6 + 10

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

* new tentative correlation for evaluating - froKD, 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 --KDcurve !bold line in ?ig.>", aro&iated by t'e equation:

- C 8.848" s'own in ?ig. 9, odified after t'ecorrelation obtained *ndrus ; Sto/oe !7888" forunceented #olocene3age soils wit' various finescontents, based on a database including 7eart'qua/es and ore t'an


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-


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0

100

200

300

400

*00

0 4 + 12 16 20 24

nt/erp0ologna

Cassino

Catania

1iumicino

enice

3ela4ny Most

?ig. . VS-KDdata airs obtained by SDMT in sands !IDO 7" atvarious sites

KD

/S1

(0s)


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E.g. at Iela$ny Most, w'ile VSvaries in t'e range788 to =88 1s, KD varies in a relatively narrowrange, ostly 7 to 7.9. 6n t'e contrary at -atania,w'ile VSis oderately variable !7983=88 1s",KDvaries in a uc' larger range !9 to 78".

T'e 'ig' disersion in ?ig. indicates t'at VSandKDreflect, besides ossibly -, ot'er roerties,so VSandKDare not interc'angeable for redicting-. T'erefore different - estiates are to bee&ected.

( /C& and KD"rusts in sandB-rust3li/eBKDrofiles 0 very siilar to t'e tyicalKDrofiles found in 6- desiccation crusts in clay 0'ave been found at t'e to of ost of t'e sanddeosits investigated by SDMT. *n e&ale ofKDcrusts !-atania" is s'own in ?ig.


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

.7 Com$arison of C&& $redi"ted %y VS and %y KD

%n order to evaluate t'e consistency of liquefactionresistance redicted by VS and by KD for a givensand, t'e --VSet'od by *ndrus et al. !788>"and t'e --KDet'od by Monaco et al. !7889",reviously described, 'ave been coared

!indirectly" by constructing a relations'i betweenVS andKDilied by t'e --VScurve for ?- 9 in ?ig. 9 !assuing bot' aging correction factorsKa andKa.C 4" and t'e --KDcurve in ?ig. >.+ot' curves aly to agnitude Mw C " and --KD!Monaco et al. 7889" forclean sands and MwC


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%n ractice, t'e coarison is liited to t'e sandlayers Bore li/ely to liquefyB, i.e. e&cluding 6-crusts and dee layers. %n t'is way, t'e scatter of t'eVS -KDdataoints is soew'at reduced !t'oug' notsubstantially", if coared to ?ig. .

T'e eaning of ?ig. is t'e following. ('en t'eVS -KD data oint lies on t'e -3equivalencecurve, bot' t'e --VSand t'e --KD et'odsrovide siilar redictions of liquefactionresistance. ('en t'e data oint lots below t'iscurve, t'e VS et'od rovides t'e oreconservative rediction. ('en t'e data oint lotsabove t'e curve, t'e KDet'od rovides t'e oreconservative rediction.

?ig. s'ows t'at t'e two et'ods 'ereconsidered for evaluating - fro VSand froKDwould rovide substantially different redictions of-. %n general, t'e VS et'od redicts -values less conservative t'an t'eKDet'od.

*not'er inconsistency observed between t'e twoet'ods concerns t'e liiting values of VSandKDfor w'ic' liquefaction occurrence can be definitely

e&cluded !asytotes of t'e --VScurve in ?ig. 9and of t'e --KDcurve in ?ig. >". Suc' values areresectively VSC 749 1s andK

DC 9.9 !for clean

sands and MwC "and Loa Prieta 4F eart'qua/e liquefaction dataoints !afterMitc'ell et al. 4>"

LIQUEFACTION

:M $R% 1989R%'

NO LIQUEFACTION

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

C'c"icS!ress%a!ioCS%

or

C'c"ic%esis!ance%a!ioC%%

KD

/S1(s)

NO LIQUEFACTION

LIQUEFACTION

:M $R% 1989R%'

C'c"icS!ress%a!ioCS%

or

C'c"ic%esis!ance%a!ioC%%

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


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100

1*0

200

2*0

300

0 2 4 6 + 10

56891C%6:; #6%9#$ort o Richmon" $:R2

$ort o :a based on available correlations.@iven t'at D& is /nown to 'ave a strong effect ont'e cyclic and ost3cyclic loading be'avior of asaturated sand, it aears t'at VS easureentswould be t'e least sensitive for distinguis'ingaong different tyes of be'avior. ?or t'is reason,%driss ; +oulanger !788>" conclude t'at it ay be

ore aroriate to view t'e VS case 'istorydatabase as roviding bounds t'at identifyconditions w'ere liquefaction is otentially 'ig'lyli/ely, 'ig'ly unli/ely and w'ere it is uncertainw'et'er or not liquefaction s'ould be e&ected. *ssuc', t'ere is still a need for an irovedunderstanding of VS based correlations and anassessent 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 basedliquefaction evaluations !for aterials wit'out largearticle si$es".

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

Moreover, researc' 'as s'own t'at KD is ore

sensitive t'an VS to factors suc' as stress 'istory,aging, ceentation, structure, w'ic' greatlyincrease, for a givenD&, liquefaction resistance and,incidentally, are felt considerably ore t'an byenetration resistance.

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


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SPT, wit'in t'e fraewor/ of t'e silifiedenetration tests vs case 'istories based aroac'!Seed ; %driss 4


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T'is oortunity aears attractive, sinceBredundancyB in t'e evaluation of - by oret'an one et'od is generally recoended.

Parallel indeendent evaluations of liquefactionresistance can be obtained fro t'e 'ori$ontal stressinde& KD and fro t'e s'ear wave velocity VSaccording to recoended --KD and --VScorrelations. T'e use of VS as an inde& ofliquefaction resistance is well /nown. T'e basis forcorrelating liquefaction resistance to KD, illustratedin detail in t'is aer, includes t'e sensitivity of KDto 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.

* reliinary validation of t'e recoended--KD et'od was obtained fro coarisonwit' field erforance dataoints obtained atliquefaction sites investigated after t'e Loa Prieta4F eart'qua/e. %n t'at case t'e --KDand --VScorrelations rovided siilar estiates.

%n general, 'owever, estiates of - by VS'ave

been found to be less conservative t'an by KD,leaving oen t'e question w'ic' - s'ould begiven greater weig't. T'e aut'ors would roend togive greater weig't to - byKDfor t'e followingreasons:

6- crusts, believed to be very unli/ely toliquefy, are unequivocally deicted by t'e 'ig'KDs, but are alost unfelt by VS. T'is suggests alesser ability of VSto rofile liquefiability.

VS easureents are ade at sall strains,w'ereas ore3ressure build u and liquefactionare ediu3 to 'ig'3strain 'enoena. T'us in

ceented soils VS can be BisleadinglyB 'ig't'an/s to interarticle bonding, t'at is eliinatedat ediu and 'ig' strains. +y contrast, KD iseasured at considerably 'ig'er strains t'an VS.

Many indications suggest at least soe lin/between KD and state araeter, w'ic' isrobably one of t'e closest ro&y ofliquefiability.

KDis sensitive not only toD&but also to factorssuc' as stress 'istory, aging, ceentation,structure, t'at greatly increase liquefactionresistance.

T'e above obviously deserves considerableadditional verification, suorted by ore welldocuented real3life liquefaction case 'istoriesw'ere VSandKDare /nown.

*-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 forroviding 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 .nd1uro$eanSym$0 on *enetration esting, *sterda, 7, F39.

Marc'etti, S. 4


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Monaco, P., Marc'etti, S., Totani, @. ; -alabrese, M. 7889.Sand liquefiability assessent by ?lat Dilatoeter Test!DMT".*ro"0 >VI 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

T-4 3 Marc'etti, S., Monaco, P., Totani, @. ; -alabrese, M.7884. T'e ?lat Dilatoeter Test !DMT" in Soil%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 4F5-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 .ndInt0 Conf0 on Site C!ara"teri?ation

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

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Maugeri Monaco SOA Liquefaction 06 SDMT