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In situ testing – current trends in geotechnical investigations

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In-situ Testing – Current Trends in Geotechnical Investigations

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In situ testing – current trends in geotechnical investigations

  1. 1. Sanjay GuptaSanjay Gupta CENGRS Geotechnica Pvt.Ltd.CENGRS Geotechnica Pvt.Ltd. New DelhiNew Delhi
  2. 2. Modern GeotechnicalModern Geotechnical EngineersEngineers Face challenges to solve various problemsFace challenges to solve various problems related torelated to –– InfrastructureInfrastructure Space utilizationSpace utilization Underground constructionUnderground construction HighwaysHighways IndustryIndustry Power sectorPower sector Hill area developmentHill area development Difficult strata conditionsDifficult strata conditions
  3. 3. Performance of the Structure should be as envisaged. Engineering SolutionEngineering Solution Higher factor of ReliabilityHigher factor of Reliability EconomicalEconomical PracticalPractical NEED to model inNEED to model in--situ behaviorsitu behavior
  4. 4. Presentation CoversPresentation Covers Current TrendsCurrent Trends ---- InIn--situ testingsitu testing –– For higher factor of reliabilityFor higher factor of reliability Modern /Advanced Testing TechniquesModern /Advanced Testing Techniques –– Static Cone Penetration TestStatic Cone Penetration Test –– Pressuremeter TestPressuremeter Test –– Aquifer / Pump Out TestAquifer / Pump Out Test –– GeoGeo--physical Testphysical Test Case StudiesCase Studies –– Projects executed byProjects executed by CENGRSCENGRS
  5. 5. Project Components of Project Foundation GeoProfesional With Advancement in Technology, We have Specialists for Various Components Human Body Parts of Body Heart Cardiologist
  6. 6. Current TrendsCurrent Trends To identify and understand the actual behavior/condition Geotechnical Investigations BH, DCPT, PLT CPT, PMT Pathalogical Investigations Blood Tests, Blood Pressure, etc. CAT Scan, MRI, etc.
  7. 7. FPS Units MKS Units SI Units Mistry Approach Architect Specialized Engineers BH, DCPT, PLT Cone Resistance (CPT) Limit Pressure (PMT) Visual/Personal Assessment Transition PhaseTransition Phase
  8. 8. Static Cone Penetration TestStatic Cone Penetration Test Power Plant 20 Tonne Capacity Near Ayodhya
  9. 9. Static Cone PenetrometerStatic Cone Penetrometer Cone tip resistanceCone tip resistance Friction jacketFriction jacket resistanceresistance Total systemTotal system resistanceresistance Friction RatioFriction Ratio
  10. 10. SCPTSCPT –– Typical ResultsTypical Results
  11. 11. Advantages of SCPTAdvantages of SCPT Continuous profile with depthContinuous profile with depth Hydraulically PushedHydraulically Pushed –– human errors minimizedhuman errors minimized Eliminates sample disturbancesEliminates sample disturbances Can use Electrical Cone / PiezoCan use Electrical Cone / Piezo--cone with Datacone with Data loggerlogger Analyze safe bearing capacity & SettlementAnalyze safe bearing capacity & Settlement directly for open foundationdirectly for open foundation Pile capacityPile capacity –– more realisticmore realistic Quality / compaction controls for embankments,Quality / compaction controls for embankments, ground improvementground improvement
  12. 12. Limitations of SCPTLimitations of SCPT Not suitable for bouldary strataNot suitable for bouldary strata Where shallow rock/hard formation isWhere shallow rock/hard formation is encountered, the utility of the test is limitedencountered, the utility of the test is limited
  13. 13. Pressuremeter TestPressuremeter Test Control Panel Gas CylinderProbe
  14. 14. Radially Expandable Probe Control Panel Inner Membrane Outer Cover Measuring Cell Guard Cell Water Gas (CO2 ) / N2 ) Volume Change Pressures Measuring Cell (Water) Guard Cell (Gas) Pressuremeter Test Unit Inflate by Coaxial Hose
  15. 15. Pressuremeter ProbesPressuremeter Probes Probes Rubber Metallic Soils (upto 25 bar) Rocks (upto 80 bar)
  16. 16. Pressuremeter ProbesPressuremeter Probes
  17. 17. Pressuremeter ProbePressuremeter Probe Probe Calibration Air Calibration Pipe Calibration Stiffness of rubber parts (Pressure) Volume loss for expansion (cc/bar)
  18. 18. Pressuremeter Control PanelPressuremeter Control Panel M.C. Gauge Differential Control G.C. Gauge Gas Cylinder Pressure Gauge Volumeter Regulator Hose to Gas Cylinder Coaxial Hose to Probe
  19. 19. ProbeProbe –– Lowering in BHLowering in BH Probe NX Casing Drill Rig
  20. 20. Pressuremeter ProbePressuremeter Probe Note increased diameter in centre
  21. 21. PMT Test at Delhi MetroPMT Test at Delhi Metro
  22. 22. Typical Test ResultsTypical Test Results V O L U M E, cc PRESSURE,bars 0 1 2 3 4 5 6 7 8 9 10 0 200 400 600 800 Corrected Curve Field Curve Air Calibration Pipe Test SoilSoil RockRock V O L U M E, cc 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 50 100 150 200 250 300 350 400 PRESSURE,bars Corrected Curve Field Curve Air Calibration Pipe Test
  23. 23. Typical PMT Profile (Soil)Typical PMT Profile (Soil) Borehole No : 1A 0 2 4 6 8 10 12 14 16 0 20 40 60 80 100 120 140 DEFORMATION MODULUS ( kg/cm2 )DEPTHBELOWGROUNDLEVEL,m 0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 LIMIT PRESSURE (bar)
  24. 24. Results of Soil ClassificationResults of Soil Classification with Limit Pressurewith Limit Pressure Soil Classification PL (kN/m2) Clay 0 – 1200 Silt 0 – 700 Firm Clay or Marl 1800 – 4000 Compressible Sand 400 – 800 Compacted Silt 1200 – 3000 Soft on Weathered Rock 1000 – 3000 Sand and Gravel 1000 – 2000 Rock 4000 – 10000 Very Compacted Sand and Gravel 3000 - 6000
  25. 25. PressuremeterPressuremeter –– AdvantagesAdvantages InIn--situ stresssitu stress--strain behavior of soil andstrain behavior of soil and rock can be evaluatedrock can be evaluated Minimum disturbance to inMinimum disturbance to in--situ conditions,situ conditions, hence quality of results is superiorhence quality of results is superior More realistic behavior / analysis for openMore realistic behavior / analysis for open & pile foundations& pile foundations In weathered rocks, where core recoveryIn weathered rocks, where core recovery is poor, pressuremeter test is the only testis poor, pressuremeter test is the only test which can give realistic datawhich can give realistic data
  26. 26. PressuremeterPressuremeter –– LimitationsLimitations Test cannot be conducted in bouldaryTest cannot be conducted in bouldary stratastrata In sandy strata, difficult to conduct the test,In sandy strata, difficult to conduct the test, due to borehole collapsedue to borehole collapse In fractured rocks, the membranes mayIn fractured rocks, the membranes may get damaged if the membranes get stuckget damaged if the membranes get stuck between the fissures.between the fissures.
  27. 27. Khalsa Heritage MemorialKhalsa Heritage Memorial ComplexComplex Anandpur SahibAnandpur Sahib (The Ajooba Project)(The Ajooba Project)
  28. 28. MemorialMemorial –– A PerspectiveA Perspective COMMEMORATING 300 YEARS OF KHALSA PANTH LAUNCHED BY GURU GOBIND SINGH
  29. 29. MemorialMemorial –– A PerspectiveA Perspective Nishan-e-Khalsa Complex C Complex A Complex B
  30. 30. Layout PlanLayout Plan
  31. 31. Site ConditionsSite Conditions Anandpur SahibAnandpur Sahib -- on the bank of Riveron the bank of River SutlejSutlej Soils are Alluvial in natureSoils are Alluvial in nature –– Foothills zone of HimalayasFoothills zone of Himalayas StratigraphyStratigraphy –– Sand mixed with pebbles / shingles withSand mixed with pebbles / shingles with Intermediate clay layersIntermediate clay layers
  32. 32. View of the SiteView of the Site
  33. 33. Typical Soil ProfilesTypical Soil Profiles
  34. 34. Foundation AnalysisFoundation Analysis Sufficient data of high quality - Greater Reliability of the parameters Analysis by four alternative methods: SPT Values Static Cone Penetration Test Results Elastic Theory Pressuremeter Test Results
  35. 35. Anandpur SahibAnandpur Sahib Settlement Analysis by Various Approaches: Foundation Size = 3m × 8m Net Bearing Pressure = 30 T/m2 N Values SCPT Data Classical Theory Pressuremeter 33.6 mm 27.0 mm 31.3 mm 13.6 mm Justify High Safe Bearing Pressures : 35~40 T/mJustify High Safe Bearing Pressures : 35~40 T/m22 for Settlements 15~35 mmfor Settlements 15~35 mm
  36. 36. Panipat RefineryPanipat Refinery
  37. 37. Panipat RefineryPanipat Refinery Bore holesBore holes –– SPT, Lab TestsSPT, Lab Tests Static Cone Penetration TestsStatic Cone Penetration Tests Pressuremeter TestsPressuremeter Tests
  38. 38. Design ProfileDesign Profile Depth (m) Soil Classification SPT (N) Value qc Value kg/cm2 Limit Pressure Value PL (kg/cm2) 0 – 10 Clayey Silt / Sandy Silt 9 30 6.1 10 – 14 Clayey Silt / Sandy Silt 10 55 8.2 14 – 17 Clayey Silt / Sandy Silt 18 70 — 17 – 30 Silty Fine Sand / Fine Sand 28 100 —
  39. 39. Open FoundationsOpen Foundations Foundation Depth (m) Foundation Width (m) Net Allowable Bearing Pressure (T/m2) Computed Settlement (mm) Classical Theory SCPT Profile Pressure- meter Results 2.0 3.0 5.7 24.9 13.9 6.0 3.0 3.0 7.3 25.0 15.4 7.7
  40. 40. Pile FoundationsPile Foundations Pile Type Pile dia. (mm) Pile length below cut-off level, m Computed axial compressive capacity, Tonnes Using c – φ from lab data Using inter- preted qu and φ values Using SCPT data Using pressure -meter data Bored Pile 500 18 75 76 138 124 Driven Pile 500 21 95 104 184 171
  41. 41. KEYPLAN RAJPURA DTCCOLONY UNIVERSITYCAMPUS KHYBERPASS CIVILLINES KAMLANAGAR JAWAHAR MALKAGANJ SABZIMANDIOLD ROSHANARAGARDEN HARIJAN NAGAR COLONY DHAKACOLONY GURUTEGBHADURNAGAR YAMUNA RIVER KOTLAFIROZ I.G.INDOOR RAJGHAT SHANTI VANA VIJAY LALQILA SADARBAZAR SOUTHBLOCK INDIA STADIUM PRAGATI PANDARAPARK SHAHFORT MADIAN GATE NATIONAL STADIUM GHAT PATELCHOWK KM12 KM 17 KM10 KM 11 KM13 KM15 KM 16 KM18 KM19 KM20 KHYBERPASSDEPOT RAILCORRIDOR E-W CORRIDOR LEGEND:- GPSSTATION GPS1 TRAVERSESTATION M1 CENTRELINEOFSTATION ISBT KHYBERPASSDEPOTLINE NORTH-SOUTHCORRIDOR RAILCORRIDOR EAST-WESTCORRIDOR MC1BMC1A KM 10.015(ENDOFCONTRACT) VISHWAVIDYALAYA CIVILLINES DELHIMAIN ISBT CHAW ARIBAZAR CENTRALSECTT. CONNAUGHTPLACE OLDSECRETARIAT PATELCHOWK NEW DELHI RAFI MARG I.P.COLLEGE KHALSA COLLEGE Underground Rail CorridorUnderground Rail Corridor
  42. 42. Pump Out / Aquifer TestPump Out / Aquifer Test Full Scale Pump Out TestFull Scale Pump Out Test –– Determine hydraulic parametersDetermine hydraulic parameters –– For Design and ConstructionFor Design and Construction Dewatering schemeDewatering scheme –– Deep excavations 15Deep excavations 15 –– 18 m for station areas18 m for station areas –– GWT not to be lowered outside the area toGWT not to be lowered outside the area to avoid subsidence of existing structuresavoid subsidence of existing structures Model the testModel the test -- RequirementRequirement
  43. 43. FullFull--scale Pump Out Testsscale Pump Out Tests Determine hydraulic Parameters:Determine hydraulic Parameters: –– Draw downDraw down –– time relationshiptime relationship –– Transmissivity of aquifer test sectionTransmissivity of aquifer test section –– Hydraulic conductivity (Permeability)Hydraulic conductivity (Permeability) –– Storage coefficientStorage coefficient –– Specific capacitySpecific capacity –– Well efficiencyWell efficiency To use in various softwares / models of hydrogeology to analyze the dewatering scheme
  44. 44. DefinitionsDefinitions Hydraulic Conductivity (K) m/sec Volume of water (m3) through unit section of soil (m2) in unit time (s) under unit hydraulic gradient. Transmissivity (T) m2/day (Productivity of an aquifer) Water capacity which flows per unit length through an aquifer under hydraulic gradient T = K x b ( b = depth of aquifer) Storage coefficient (%) Volume of water it takes / releases per unit surface area of aquifer under unit change of head. Specific capacity Discharge for unit time for unit draw down c = Q / s
  45. 45. SubSub--Strata FormationsStrata Formations AlluviumAlluvium RockRock AlluviumAlluvium--RockRock
  46. 46. Testing ProcedureTesting Procedure Installation of PW & OWInstallation of PW & OW –– Well Depths, selection of slotted / blankWell Depths, selection of slotted / blank portions etc.portions etc. Step draw down testStep draw down test –– SDD testSDD test Constant discharge testConstant discharge test –– CD testCD test Recuperation / Recovery testRecuperation / Recovery test
  47. 47. Pump WellPump Well –– AlluviumAlluvium
  48. 48. Pump Well InstallationPump Well Installation
  49. 49. Pump Well Installation DetailsPump Well Installation Details
  50. 50. Test in ProgressTest in Progress
  51. 51. Flow MeterFlow Meter
  52. 52. Step Draw Down TestStep Draw Down Test Steps estimated on maximum yield of the wellSteps estimated on maximum yield of the well based upon well development databased upon well development data Discharge is increased in steps of 100 min.Discharge is increased in steps of 100 min. Discharge level controlled by Control Valve andDischarge level controlled by Control Valve and Flow MeterFlow Meter PurposePurpose –– To estimate discharge for CD test for response ofTo estimate discharge for CD test for response of aquiferaquifer –– To estimate well parametersTo estimate well parameters
  53. 53. Time vs. Step DrawTime vs. Step Draw--Down atDown at Pump WellPump Well
  54. 54. Discharge vs. Step DrawDischarge vs. Step Draw-- DownDown
  55. 55. Specific Draw Down vs.Specific Draw Down vs. DischargeDischarge
  56. 56. Constant Discharge TestConstant Discharge Test Select constant discharge value to stress aquiferSelect constant discharge value to stress aquifer for proper response from SDD testfor proper response from SDD test Pump well continuously pumpedPump well continuously pumped -- Water levelWater level recorded in PW and OW at regular intervalsrecorded in PW and OW at regular intervals Test continues till near steady state / equilibriumTest continues till near steady state / equilibrium conditioncondition PurposePurpose –– To obtain hydraulic characteristics of the aquiferTo obtain hydraulic characteristics of the aquifer within the radius of influence of Pump wellwithin the radius of influence of Pump well
  57. 57. C.D. TestC.D. Test –– Typical ResultTypical Result 0.001 0.01 0.1 1 10 1 10 100 1000 10000 Time, min Correcteddrawdownsc,m 3.86 Time vs. Corrected Draw Down at PWTime vs. Corrected Draw Down at PW
  58. 58. Recovery TestRecovery Test After CD test is complete, Pump isAfter CD test is complete, Pump is stoppedstopped Allow water table to riseAllow water table to rise Take Water level readings in sameTake Water level readings in same sequence as for CD testsequence as for CD test Test continues till water level rises up toTest continues till water level rises up to static levelstatic level
  59. 59. AnalysisAnalysis Bottom plugged with bottom blank casing portionBottom plugged with bottom blank casing portion –– Assumes only radial flowAssumes only radial flow Analysis AssumesAnalysis Assumes –– Uniform homogeneous soil mass with uniformUniform homogeneous soil mass with uniform propertiesproperties –– Permeability of strata below Pump well Very lowPermeability of strata below Pump well Very low As such analysis assumes fully penetrating wellAs such analysis assumes fully penetrating well –– drawdown to be correcteddrawdown to be corrected AnalysisAnalysis –– Various approachesVarious approaches –– Theis MethodTheis Method –– CooperCooper--Jacob MethodJacob Method
  60. 60. Aquifer ParametersAquifer Parameters ( )2 c 2 QW u T (m day) 4 s T K (m sec) b 4AT t u S r = π = = 2 c s Corrected Drawdown, s s 2b = − Theis MethodTheis MethodCooperCooper--Jacob MethodJacob Method 2 0 2 2.3 Q T (m day) 4 s T K (m sec) b 2.25T t S r = πΔ = =
  61. 61. AlluviumAlluvium--Rock FormationRock Formation Rock at 15 M below G.L.Rock at 15 M below G.L. GWT at 3.0 M depthGWT at 3.0 M depth Excavation to 18~20 M depthExcavation to 18~20 M depth Water to be pumped out from rock strataWater to be pumped out from rock strata –– To study response in alluviumTo study response in alluvium Rock formation highly fractured, weathered,Rock formation highly fractured, weathered, boulders at interfaceboulders at interface Wells redesigned to suit requirementsWells redesigned to suit requirements –– PW sealed in soils & OW in rock layersPW sealed in soils & OW in rock layers
  62. 62. Pump Well : AlluviumPump Well : Alluvium--RockRock
  63. 63. Observation Well : AlluviumObservation Well : Alluvium-- RockRock
  64. 64. Summary of ResultsSummary of Results Formation Method Aquifer Parameters Coefficient of Permeability from Packer permeability tests in Boreholes (cm/sec.) Tav (m2/day) Kav (cm/sec) Sav Alluvium Strata (Delhi Silt) Theis 65 3.5 × 10−3 5 × 10−3 7.0 × 10−5 Cooper-Jacob 71 4.0 × 10−3 4 × 10−3 Rock Strata in Soil-Rock Formation (Delhi Quartzite) Theis 385 2.0 × 10−2 8 × 10−3 1.7 × 10−3 Cooper-Jacob 420 2.2 × 10−2 9 × 10−3
  65. 65. Geophysical InvestigationsGeophysical Investigations Electrical Resistivity TestElectrical Resistivity Test River Chairala, NepalRiver Chairala, Nepal
  66. 66. ERT as Investigation ToolERT as Investigation Tool FAST TRACK Projects on infrastructureFAST TRACK Projects on infrastructure –– bridgesbridges –– Preliminary assessmentPreliminary assessment –– Detailed assessmentDetailed assessment In bouldersIn boulders -- soil matrix cost & time savingsoil matrix cost & time saving can be substantialcan be substantial –– No. of bore holes can be reducedNo. of bore holes can be reduced Used in conjunction with BH data toUsed in conjunction with BH data to estimate stratigraphy & continuityestimate stratigraphy & continuity
  67. 67. Schematic of Resistivity TestSchematic of Resistivity Test Soil Resistivity Unit Current Meter Battery Volt Meter WennerElectrode Configuration A M N B GL GL a a a I1 I2 P2 P1 II11 and Iand I22 are current electrodesare current electrodes PP11 and Pand P22 are potential electrodesare potential electrodes For WennerFor Wenner Configuration,Configuration, ApparentApparent Resistivity,Resistivity, ρρaa = 2= 2ππaV/IaV/I
  68. 68. Inverse Slope MethodInverse Slope Method Spacing/App.Resistivity,a/ρα Slope = 1/ρ1 Slope = 1/ρ2 Slope = 1/ρ3 h1 h2 Electrode Spacing, a
  69. 69. InterpretationInterpretation Data matching techniqueData matching technique Interpreted stratigraphyInterpreted stratigraphy –– average over theaverage over the spread investigatedspread investigated Scatter of the data points on the “a versus a/Scatter of the data points on the “a versus a/ρρa plot” needs careful interpretationplot” needs careful interpretation If three points lie on a straight line, one can beIf three points lie on a straight line, one can be fairly confident that the interpretation is correct.fairly confident that the interpretation is correct. Resistivity ranges for the different soil typesResistivity ranges for the different soil types overlapoverlap Needs experience & judgment for interpretationNeeds experience & judgment for interpretation
  70. 70. True Resistivity for AnalysisTrue Resistivity for Analysis True Resistivity, ohm-m Interpreted Stratigraphy 30 – 75 Sand and silty sand 10 – 50 Stiff clay and sandy silt 50 – 100 Sand with gravel/pebbles > 100 Hard clay > 200 Pebbles and boulders intermixed with sand
  71. 71. Interpreted StratigraphyInterpreted Stratigraphy River Chairala, NepalRiver Chairala, Nepal True Resistivity, (ohm-m) 30 55 High High 100 True Resistivity, (ohm-m) 30 55 High High 100 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 10 20 30 40 50 Electrode Spacing, a (m) ElectrodeSpacing/ApparentResistivity,a/ρa Interpreted Stratigraphy Interpreted Stratigraphy Silty Sand Clayey Silt Clayey Silt Pebbles & Boulders intermixed with Sand Pebbles & Boulders intermixed with Sand
  72. 72. Generalized Site StratigraphyGeneralized Site Stratigraphy River CharailaRiver Charaila
  73. 73. AdvantagesAdvantages Stratigraphy & thickness of various layersStratigraphy & thickness of various layers Confirm continuity & depth of variousConfirm continuity & depth of various layerslayers No. of bore holes can be reducedNo. of bore holes can be reduced –– Reduction in investigation Time & costReduction in investigation Time & cost
  74. 74. LimitationsLimitations Knowledge of geology/stratigraphyKnowledge of geology/stratigraphy –– forfor interpretationinterpretation Steeply dipping or variable strataSteeply dipping or variable strata –– may result inmay result in erratic interpretationerratic interpretation Location under waterLocation under water –– test not possibletest not possible Geotechnical parametersGeotechnical parameters -- c andc and φφ, density, etc., density, etc. not obtainednot obtained Not an alternative to bore holesNot an alternative to bore holes Interpreted stratigraphy as guideInterpreted stratigraphy as guide –– may varymay vary from actualfrom actual
  75. 75. Concluding RemarksConcluding Remarks In situ testing provides realistic dataIn situ testing provides realistic data Modern testsModern tests –– SCPT & PMT provideSCPT & PMT provide superior datasuperior data Geophysical testsGeophysical tests –– ERT useful inERT useful in bouldary stratabouldary strata Aquifer testAquifer test –– tool for dewatering schemetool for dewatering scheme Selection of testsSelection of tests –– AN ARTAN ART
  76. 76. Concluding RemarksConcluding Remarks The geotechnical engineer has to becomeThe geotechnical engineer has to become one with the soul of the soilone with the soul of the soil –– Be a part of the soil: have feel of the soilBe a part of the soil: have feel of the soil –– Feel the stresses: deform along with itFeel the stresses: deform along with it The solution to the problem will emergeThe solution to the problem will emerge from the soil itselffrom the soil itself Use modern inUse modern in--situ tests for higher factorsitu tests for higher factor of reliabilityof reliability Interpretation is AN ARTInterpretation is AN ART
  77. 77. Thank U!Thank U!
  78. 78. Interpreted StratigraphyInterpreted Stratigraphy River Chairala, NepalRiver Chairala, Nepal 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 10 20 30 40 50 Electrode Spacing, a (m) ElectrodeSpacing/ApparentResistivity,a/ρa True Resistivity, (ohm-m) 30 55 High High 100 True Resistivity, (ohm-m) 30 55 High High 100 Pebbles & Boulders intermixed with Sand Pebbles & Boulders intermixed with Sand Silty Sand Clayey Silt Clayey Silt 0 5 10 15 20 25 30 40 35
  79. 79. Interpreted StratigraphyInterpreted Stratigraphy River Chairala, NepalRiver Chairala, Nepal

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