Foundation /Geotechnical Engineering Types of Tests Equipments Used Basic Design Parameters

Ing. Enyo Matrevi

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

Geotechnical EngineeringSite Investigation & Field Testing

Laboratory Testing & Test Interpretation

Engineering Design

Site Investigation and Field TestingReview Available InformationIdentify Required Materials Prop.Plan Site InvestigationConduct Field TestingDescribe Samples Develop Subsurface ProfilesReview Design Objectives

SITE SAMPLING

Laboratory Testing & Test Interpretation

Select Samples for Performance TestingConduct Laboratory TestingReview Quality of Laboratory TestingSelect Material Properties

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.

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

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

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

PERCUSSION DRILLING RIG

ROTARY RIG

Type of TestsField TestsStandard Pen. Tests (SPT)Cone Pen. Tests (CPT)Vane Test (c, )Plate Load TestGeophysical TestPile Load TestPiezometer TestDynamic Cone Pen. Test

Type of TestsLaboratory TestsDirect Shear Tests1-D Consolidation TestTriaxial TestGrain size distributionAtterbergs LimitspH testsUnit WeightOrganic ContentRock Uniaxial TestSwell TestsPoint Load Strength TestMoisture content Test

GEOPHYSICAL TESTING IN PROGRESS

PLATE LOAD TESTING IN PROGRESS

PLATE LOAD TESTING IN PROGRESS

Basic Design Parameters

Bearing Capacity Estimation

Settlement

Permeability Characteristics

Elastic Modulus

Uniaxial Compressive Strength

Rock Quality Designation

Chemistry of Soil/Rock

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

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

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.

END OF PRESENTATION