The Observational Method in Civil Engineering: Minimising Risk, Maximising Value

The Art of Achieving AgreementKey FactorsThe Power of Progressive ModificationSummaries of Featured Case HistoriesReferencesChannel Tunnel Cut and Cover Works (1988–1990)IntroductionKey Aspects of Design and ConstructionOverviewGeologyDesign UncertaintiesAchieving Agreement to Use the OMCreating OpportunityFinding the KeyImplementation of the OMDevelopment of Progressive ModificationConstruction Sequence, Form and GeometryDesign ConstraintsAddressing UncertaintyInstrumentation and MonitoringCastle Hill East – The OM Stage 1: InitiationMeasured Performance at CHESugarloaf Hill – The OM Phase 2: DevelopmentCastle Hill West – The OM Phase 3: ConclusionLandslip LoadingConnection with the NATM TunnelsInterface CoordinationThe OM and ‘Most Probable’ ConditionsConclusionsReferencesMansion House (1989–1991)IntroductionKey Aspects of the Design and ConstructionFoundations in the Building’s HistoryThe Challenge Presented by the DLRAchieving Agreement to Use the OMAddressing ComplexityCreating the Solution through the OMIntroduction of the OM Traffic Light SystemImplementation of the OMManaging RiskThe Profound Influence of Soil/Structure InteractionInstrumentation and MonitoringTemperature-Induced Cyclic MovementsDevelopment of Progressive ModificationCritical Observations, Trigger Levels and ContingenciesResultsOverviewDetailed AssessmentThe Benefit of HindsightConclusionsReferencesLimehouse Link (1991–1993)IntroductionKey Aspects of Design and ConstructionOverviewGeologyOriginal DesignValue EngineeringAchieving Agreement to Use the OMOvercoming Traditional BarriersThe Key to ConsensusImplementation of the OMExtending the Process of Progressive ModificationSequence for Each Implementation of the OMObservations, Trigger Levels and ContingenciesMeasured PerformanceIncreasing Beneficial Design ChangesPersonnel and CommunicationAchieving Simple and Effective MonitoringConstruction Plant and ResourcesLimehouse Basin ConstructionReaching the Practical Limits of the OMMonitoring Becomes IntensiveImplementation of the OM in Limehouse BasinAdded Value Still AchievedRisk and InsuranceConclusionsReferencesHeathrow Express Cofferdam (1994–1995)IntroductionKey Aspects of Design and ConstructionOverviewGeology - Conditions Prior and Post CollapseContractual ConditionsThe CofferdamAchieving Agreement to Use the OMSafety and InnovationProgressive Modification Offers the Way ForwardImplementation of the OMThe Recovery SolutionCofferdam ConfigurationInnovations in Piled Wall Design and ConstructionDesign DevelopmentA Bespoke Design for Progressive ModificationObservations, Trigger Levels and ContingenciesMeasured Performance and Design ImprovementsConclusionsReferencesHeathrow Airport Multi-Storey Car Park 1A (1995–1996)IntroductionKey Aspects of Design and ConstructionOverviewGeologyTunnel ConstructionCar Park StructureAchieving Agreement to Use the OMImplementation of the OMTraffic Lights, Trigger Levels and ContingenciesRisk AssessmentsPredicted Ground MovementsMeasured SettlementsEffects on the Building and Remedial MeasuresDamage AssessmentRemedial MeasuresStructural Response: Actual vs PredictedBackground to the Risk AssessmentEvaluation of Actual ResponseKey Lessons LearnedConclusionsA Triple IronyBeware the Oddball – Reflections on Peck (1998)ReferencesBoston Central Artery Tunnel Jacking (1991–2001)IntroductionKey Aspects of Design and ConstructionThe ProjectGeologyOriginal Design ConceptInnovations in Tunnel JackingAchieving Agreement to Use the OMA Dramatic Simplicity‘A Rose by Any Other Name’Implementation of the OMThe Primary ObjectiveSolving the Spatial ChallengesThe Process for Tunnel JackingConstruction Activities Causing Ground MovementsInstallation of Diaphragm Walls Forming the Thrust PitsJet Grouting of the Low Level In-Situ StrutBulk Excavation of the Thrust PitsInstallation of Vertical Freeze PipesHeave and Lateral Movement of the Ground during FreezingGround Movements during Tunnelling OperationsLonger-Term Ground Movements during Thawing and ConsolidationInstrumentation and MonitoringRailway Track MonitoringDiaphragm Wall MonitoringGround Movement and Groundwater MonitoringManaging InterfacesFostering a Collaborative ApproachTeamworkExtending the Limits of Progressive ModificationResultsConclusionsReferencesIrlam Railway Embankment (1996–1998)IntroductionKey Aspects of Design and ConstructionOverviewGeologyBridge AssessmentProject ConstraintsEvaluation of Embankment OptionsIdentifying Viable OptionsPotential Adverse Effects on Bridge FoundationsAchieving Agreement to Use the OMImplementation of the OMTrigger Levels and Contingency MeasuresInstrumentation and MonitoringPre-load Embankment ConstructionRemoval of Pre-Load and EPS Embankment ConstructionConclusionsReferencesHeathrow Airport Airside Road TunnelIntroductionKey Aspects of Design and ConstructionPortal Structures and TunnelsGeologyBase Case DesignConstruction SequenceRetaining Wall DesignAchieving Agreement to Use the OMPromoting InnovationAddressing the Issue of PrecedentImplementation of the OMA Big Challenge at a Small ScaleThe Breakthrough ConceptInstrumentation, Trigger Levels, Contingencies and Measured PerformanceInnovation in Blinding StrutsInterface with the Piccadilly Line TunnelImplementing InnovationConclusionsReferencesRaising the 133 m High Triumphal Arch at the New Wembley Stadium (2002–2004)IntroductionKey Aspects of Design and ConstructionOverviewFoundations and GeotechnicsArch RaisingAchieving Agreement to Implement the OMCreating OpportunityAssessment of Foundation Behaviour during Arch RaisingPreliminary Pile Load TestsEstablishing Trigger Levels and Contingency MeasuresFoundation AnalysisTrigger Levels and Contingency PlansImplementation of the OMInitial SurveysObserved Pile Group DeformationConclusionsReferencesCrossrail Blomfield Box (2012-2015)IntroductionKey aspects of Design and ConstructionAchieving Agreement to Use the OMPotential HazardsDesign ConditionsImplementation of the OMDewatering Systems - Potential Failure ScenariosInstrumentation and MonitoringTraffic Light System for the О/ИDewatering System, Observations Outside of the Blomfield BoxDisplacement of Contiguous Pile Retaining WallDewatering System, Observations Inside the Blomfield BoxDewatering System, Modifications during Final Phase of ExcavationSummary of Changes Introduced through Implementation of the О/ИConclusionsReferencesCrossrail Moorgate Shaft (2012–2014)IntroductionKey Aspects of Design and ConstructionAchieving Agreement to Use the OMDesign Objectives and ConstraintsCreating OpportunityVerification ProcessImplementation of the OMKey Steps and ActivitiesVerification Point 1Verification Point 2Verification Point 3Summary of Changes Introduced through Implementation of the OMReflections on the Role of Analysis and Bayesian UpdatingConclusionsReferencesReflections on the Advantages and Limitations of the Observational MethodThe Legacy of Terzaghi and PeckAdvantages and Limitations of the OMLessons Learned from the Case HistoriesThe Importance of SimplicityKey LimitationsHeathrow Terminal 5 Tunnels – An Illustrative Case HistoryProgressive Modification – Solving the Issue of the ‘Most Probable’ReferencesSome Observations on the Way ForwardThe 1996 OverviewCommercial and Contractual EnvironmentOverviewDesign and BuildDeveloping Greater CollaborationValue Engineering ClausesInstrumentation and MonitoringGeneral ConsiderationsPerformance Limits and Traffic LightsProgressive Modification – A Comprehensive ApproachPeer ReviewRecommendations for OM PractitionersReferences
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