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Page1RealTimeMonitoringattheOlive8ExcavationByRichardJ.Finno1M.ASCE,MiltosLangousis2,DavidG.Winter3,M.ASCE,MatthewW.Smith,M.ASCE4andKingH.Chin,A.M.ASCE51Professor,DepartmentofCivilandEnvironmentalEngineering,NorthwesternUniversity,Evanston,IL60208,r-finno@northwestern.edu2ResearchAssistant,DepartmentofCivilandEnvironmentalEngineering,NorthwesternUniversity,Evanston,IL60208,m-langousis@northwestern.edu3President,GeoEngineers,Inc.,Plaza600Building,Suite1700,Seattle,WA981014Associate,GeoEngineers,Inc.,8410154thAvenueNE,Redmond,WA,98052,msmith@geoengineers.com5SeniorEngineer,GeoEngineers,Inc.,Plaza600Building,Suite1700,Seattle,WA98101,kchin@geoengineers.comABSTRACT:TherealtimemonitoringfortheOlive8projectinSeattleisdescribed.Thisprojectinvolvedconstructionofa39storystructurewith5levelsofbelowgradeparking.The76ftdeepexcavationnexttoanadjacentbuildingrequiredahybridsupportsystemconsistingoflargesoldierpileswithtightlyspacedsoilnailsintheupperportionandsteeplyinclinedtiebackanchorsinthelowerportion.BecausetheCityofSeattlelimitedlateralmovementsto1inch,engineersimplementedadetailedmonitoringsystem.Conventionalinclinometersandopticalsurveypointsweresupplementedbyrealtimemonitoringconsistingofawebcameraandanautomatedtotalstation.Thispapersummarizesthephilosophybehindthereal-timeinstrumentationandshowshowthetotalstationdatacomplementedtheconventionalinclinometerdata.Datareductiontechniquesaredescribedandperformancedataarepresented.Finiteelementsimulationsoftheexcavationprocessshowedthecriticalobservationwasthecantilevermovementsatthetopofthesupportwalls.Surveyprismsweremountedatthreesuchlocationsalongthewestwalltoproviderealtimeperformancedata.Aprojectwebsiteallowedallinterestedpartiesaccesstothedata.Thepaperillustrateshowrealtimemonitoringandcarefuldesigncanbeusedtogreateffect.INTRODUCTIONTheOlive8projectinSeattle,WAinvolvedtheconstructionofa39storystructurewith5levelsofbelow-gradeparking.The76ftdeepexcavationwaslocatedadjacenttotheQwestbuildingfoundedonamatatadepthof52ft.DuringthepermittingPage2process,theCityofSeattlestipulatedthatifthelateralmovementswereobservedtobeinexcessof½inchbetweentwosuccessivereadingsorifthetotalwallmovementsexceeded1inch,theconstructionoftheshoringwallwouldbestoppedtoevaluatethecauseofthemovementandtoestablishthetypeandextentofremedialmeasuresrequired.Basedonpastperformancedataofexcavationsthroughsimilarsoilconditions,typicaldeflectionsforexcavationsofthisheight(CloughandO’Rourke1990)wereexpectedtovaryfrom0.001Hto0.003H,or¾inchtoabout2.5inches.Thereforeparticularattentionwaspaidtodesigningthesupportsystemtolimitthemovementstolessthan1inch.Tomeettheserequirements,thewalladjacenttotheQwestbuildingwasdesignedwithahybridsupportsystemconsistingoflargesoldierpileswithtightlyspacedsoilnailsintheupperportionandsteeplyinclinedtiebackanchorsinthelowerportion.Tofacilitatetimelydataacquisitionandevaluationduringconstruction,arobotictotalstationautonomouslycollected3-dimensionalmovementsofprismsestablishedatthetopofthesupportwall.Thesedatawereplacedautonomouslyonawebsitethatallowedallinterestedpartiesaccesstotheinformation.Thetotalstationdatawerecombinedwithlateralmovementsbehindthesupportwallmeasuredwithconventionalinclinometers.Becausedesigncalculationssuggestedthecantilevermovementsatthetopofthewallcouldlikelyhavebeenthelargestmovementsthatwouldoccur,thecombinationofthetwotypesofdatawouldallowessentiallyrealtimeevaluationoftheeffectsofconstructiononthegroundmovements.ThispaperdescribestheOlive8excavation,discussesthedesignstudiesusedtodeveloptheinstrumentationapproach,presentstheinstrumentationanddataacquisitionsystemsemployedatthesite,summarizestheperformanceofthesupportsystemandcomparesthedesignpredictionswiththeobservedresponses.SITEDESCRIPTIONThedesignoftheexcavationforthe8thandOlivedevelopmentinSeattlepresentedanumberofchallengesduetothepresenceoftheadjacentQwestbuilding.A16ftalleyseparatedtheOlive8excavationandtheQwestbuilding,immediatelytothewest.TheQwestbuildingextendsapproximately52ftbelowgradeandissupportedonaperimeterstripfootingandamatfoundationforthecoreofthestructure.Thedesignbearingpressureofthesefoundationswas10ksf.Existingburiedpowerandcommunicationsutilitiesarelocatedinthealleyalongwithfiveutilityvaults.Becauseofthemovementconstraintsimposedbytheseconditions,thedesignoftheexcavationsupportforthatwalldifferedfromtheotherthreewalls.AcrosssectionthroughtheexcavationadjacenttotheQwestbuildingisshowninFigure1.Theshoringsystemforthewestsupportwallconsistedofacombinationofsoldierpiles,soilnailsandtiedbackgroundanchors.ThesoldierpileswereW24x162sectionsspacedatapproximately8ftcenters.Theupperportionofthealleysoilswasreinforcedwithahighdensitysoilnailconfigurationtotheelevationwherethetiebackanchorswereinstalled.Typically,9rowsofsoilnailswereinstalledat3ftverticalby4fthorizontalspacing.Thesoilnailswereangled15degreesbelowthehorizontalPage3FIG1.SubsurfaceConditionsandSupportSystematWestWallandconsistedofno.10rebargroutedintoarotaryaugered,8-inchdiameterhole.Thedrillingstoppedapproximately1f