Foundation_Geotechnical Engineering - GHA
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Transcript of Foundation_Geotechnical Engineering - GHA
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Foundation /Geotechnical Engineering Types of Tests Equipments Used Basic Design Parameters
Ing. Enyo Matrevi
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Foundation/Geotechnical EngineeringSoil Mechanics Soil EngineeringRock MechanicsGeology
FoundationsEvery civil engineering structure/building/bridge/dam/slope/ embankment founded on or below the surface of the earth
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Geotechnical EngineeringSite Investigation & Field Testing
Laboratory Testing & Test Interpretation
Engineering Design
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Site Investigation and Field TestingReview Available InformationIdentify Required Materials Prop.Plan Site InvestigationConduct Field TestingDescribe Samples Develop Subsurface ProfilesReview Design Objectives
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SITE SAMPLING
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Laboratory Testing & Test Interpretation
Select Samples for Performance TestingConduct Laboratory TestingReview Quality of Laboratory TestingSelect Material Properties
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Engineering DesignPerform Design
(Design Engineer has necessary information related to soil and rock properties to complete the design)
Evaluating whether to employ cohesive or granular analysis/interpretation on physical and mechanical properties of soil and rock.
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Summary of Information needs for Testing
Type of FoundationEngineering EvaluationInformation RequiredField TestingLaboratory TestingShallow FoundationBearing CapacitySettlement Shrink/ SwellChemistryScour Extreme LoadingSoil ProfileShear Strength par.CompressibilityShrink/SwellStress HistoryChemical CompositionSeasonal VariationUnit weightsGeologic MappingVane Shaer TestSPT (granular Soil)CPTRock CoringNuclear DensityPlate Load TestGeophysics testing1-D Oedometer testDirect shear testTriaxial testsGrain Size distributionAtterbergspH, ResistivityMcUnit WeightOrganic ContentRock Uniaxial comprPoint Load Strength testDeep FoundationPile End bearingPile Skin FrictionSettlement Lateral Earth pressuresScour Extreme LoadingVibrationPresence of BouldersSoil ProfileShear Strength par.CompressibilityShrink/SwellStress HistoryChemical CompositionSeasonal VariationUnit weightsGeologic MappingHorizontal Earth PressureFriction parametersSPT (granular SoiisPile Load Test CPTVane TestingPiezometerRock Coring(RQD)Geophysics testing1-D Oedometer testDirect shear testTriaxial testsGrain Size distributionAtterbergspH, ResistivityMcUnit WeightOrganic ContentRock Uniaxial comprPoint Load Strength testSlake DurabilityFriction Test
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Checklist Items for Site Investigation
AccessibilityEasyDifficultSite HydrologySurface Water/Dry/DesertPrior InformationMaps/Files /Memmoirs/City Records/InterviewsVisit To SiteDate/TimeWeather ConditionSite DrainageNatural,Artificial drainsRun Off Features; Erosion/ponding/pipingTopo DataSite/State/Country SurveysGround CoverGrass/Rock Outcrop/Debris/Concrete/Asphalt/OtherSoil/Rock ConditionSurface SoilsSubsurface Soils: Surface Rocks/Type of Rocks/Rock featuresGeologic InformationGeologic mapsField mappingGeologic surveysExisting TerrainLevel/Sloping/Steep./Rolling/Mountainous/HillyInvestigative OperationsTest PitsBoreholesCased Holes UtilitiesOverhead linesGas linesManholesPower/Sewer linesElectromagnetic readings
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Equipments UsedPits & Trenches (pick axes & shovels)
Percussion Rigs
Rotary Rigs
Auger Boring
Piezometer
Plate Load test
Dynamic Cone Penetrometer testTo determine structures of complex formations, obtain samples
To Locate soils/rock seams
To obtain rock and determine rock properties
In soil and soft rock; to identify geologic units & water contentTo extract water and determine water propertiesDetermine settlement and modulus characteristics of soil
To assess relative density of underlying soils
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PERCUSSION DRILLING RIG
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ROTARY RIG
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Type of TestsField TestsStandard Pen. Tests (SPT)Cone Pen. Tests (CPT)Vane Test (c, )Plate Load TestGeophysical TestPile Load TestPiezometer TestDynamic Cone Pen. Test
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Type of TestsLaboratory TestsDirect Shear Tests1-D Consolidation TestTriaxial TestGrain size distributionAtterbergs LimitspH testsUnit WeightOrganic ContentRock Uniaxial TestSwell TestsPoint Load Strength TestMoisture content Test
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GEOPHYSICAL TESTING IN PROGRESS
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PLATE LOAD TESTING IN PROGRESS
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PLATE LOAD TESTING IN PROGRESS
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Basic Design Parameters
Bearing Capacity Estimation
Settlement
Permeability Characteristics
Elastic Modulus
Uniaxial Compressive Strength
Rock Quality Designation
Chemistry of Soil/Rock
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Bearing Capacity EstimationTwo approaches are often used in the estimation of bearing capacities.
The first approach utilizes the Cu / relationship obtained from laboratory shear strength tests on undisturbed clayey/silty samples
the second approach employs N-values from standard penetration tests (SPT) to obtain Cu and in the absence of laboratory Cu and values.
For the Cu / relationship, the general ultimate bearing capacity (Qult) equation is given as
Qult = Cu Nc Sc + z Df Nq Sq +
where Df = foundation width, Cu = undrained cohesion of the soil, ,= density of soil, Nc, Nq N, = bearing capacity factors and, Sc, Sq, S = shape factors, N and S factors are obtained using , the angle of shear resistance.Other equations are Qall = N/0.08 for D>0 Cu = 29 N0.72 BS 8004 CP 2004
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SettlementEstimationFrom Oedometer Consolidation tests results, probable settlement estimation are made using the relationship;Sf = Mv Ho k = Cv Mv Yw
Where: Mv = coefficient of volume compressibility, = effective stress and Ho = thickness of compressible layer below foundation
Other equations are;
S = q B I (1 v2) Es
Cc = 0.009(LL-10%) S = 2.25qB(1-v2)/Ed
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Permeability CharacteristicsK = C (d10)2 = Cv Mv 0.31x10-9 = d(10)2/100 m/s
where k = Permeability coefficient C = coefficient ranging from 0.4 1.2 from grain size distribution D10 = effective grain size passing 10% on graph
Consolidation test could also be used to determine k.
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END OF PRESENTATION