4FoundationsFoundation Engineering- Evaluating the ability to support a given structural load and designing the substructure or transition member needed to support the construction. To transfer the structural loads safely into the ground.This means dealing with forces and soil pressures. The need for deep excavations.
5Foundations Spread Footings Driven Piles Caissons or Drilled Shafts Proper compaction under the footingDriven PilesTypes of pilesWoodConcreteSteelComposite-Pile DriversDrop HammerMechanical- Hydraulic, diesel, steamVibratoryCaissons or Drilled ShaftsCofferdams
6Review Plans & Specifications Consistency with geotechnical reportReduce confusion during constructionWithout Differing Site Conditions clause contractor responsibleRead the report in response to what is underground.Understand prescribed method, consistency with soils reportSite InvestigationsEnvironmental restrictionsSite conditions at each and every locationThe report has pertinent information- follow it.Compaction testingUnderstanding moisture contentProper proctor
8Importance of Geotechnical Studies Provide efficient foundations systemsImprove bid accuracyReduce change ordersReduce long term problems
9Geotechnical/Soils Reports Recommendations Suitability of on site soil for structural fillBearing capacityFoundation typeLateral earth pressuresPavementsDrainageSeismic
10Steps for Geotechnical Study Explore site conditionsPerform lab testingPerform engineering analysisPrepare reportAssist with plans and specificationsConstruction observations
11Soil Report Borings or test pits To lab for: Moisture content GradationsProctor testConsolidation, direct shear, triaxial
12Pile & Pile Driving Site Investigation Type & weight of structure Soil propertiesDepth of stratumVariations of stratum depthAvailability of piling typeAvailability of pile driverAvailability of experience in driving pile
13Pile & Pile Driving (Site Investigation cont) Comparative placement costEPA & OSHA regulationsDepth of excavation for placement of equipment ie building footingLocation of piling ie river, lake, oceanNoise & VibrationAdjacent structures
15Pile & Pile Driving Pile Caps & Grade Beams Piles are clustered then capedNumber of piles per cap are determined by the load bearing capacity of the soil.From the cap comes a column or bent.Piles can be connected by grade beams
18Caisson or Cofferdam What’s the difference? Caisson- Boring or drilling a hole and filling with concrete.Cofferdam- A temporary boxlike structure used to hold back water or earth while work is being done inside it.
22EXCAVATION HORIZONTAL & VERTICAL LAYOUT BEGIN EXCAVATION SWELL AND SOIL TYPESUNSUITABLE SOILSTRUCTURAL FILLSITE DRAINAGEDEWATERINGCOMPACTIONBACKFILLSAFETYMECHANICAL & ELECTRICAL
23Excavation Wall Bracing No matter what restraining system is used to stabilize the sides of an excavation, the walls will have to be braced against lateral pressures exerted by the surrounding soil and water.Shoring for trenches (trench boxes)Lateral forces surrounding the structureSlope backDifferent shoring systemsTiebacks (rock and earth)
24Protection of Excavations Lateral Forces Deep Excavations Slope Back- Usually 2:1, The angle of repose at which a soil material will stand without movingInterlocking Sheet PilingSteel Soldier Piles- H beam with laggingConcrete Slurry walls-Shotcrete (pneumatically projected at high velocity onto a surface)
25Other piling terminology Battered pile- A pile driven somewhat at an angle so as to resist horizontal forces.Kelly bar- The equipment on the pile driver that determines the height of the pile to drive.
29Terminology In the industry terms can mean different things. Toe- (1) Any protection from the base of a construction or object to give it increased bearing and stability. (2)That portion of sheeting below the excavated material. (3) To drive a nail at an oblique angle. (4) The junction between the base metal and the face of a filled weld. (5) The part of the base of a retaining wall that projects beyond the face away from the retained material.
35Excavation Need for Deep Foundations Removing ground water or dewateringAmount of material to be removedSoil swell percentageFor removal and replaceTons to cubic yardsProtection of ExcavationSheet PilingSoldier PilesConcrete Slurry WallsExcavation Wall BracingSlope backShoringTiebacks
36Foundation Sequencing Drive Piling- Excavate> >[Slope protection/shoring system]> Layout Piles>Drive Piles>Cut off piles>Fine grade/Compact>Structural Fill> Backfill to follow foundation systemDrilled Piling (concrete)- Excavate> >[Slope protection/shoring system]> Layout Piles>Auger piling>Fabricate Cage>Set reinforcing cage>Pour concrete pile>Fine grade/Compact>Structural Fill> Backfill to follow foundation systemSpread Footings-Excavate>[Slope protection/shoring system]>Layout>Fine grade/Compact>Structural Fill> Backfill to follow foundation system