51 PILE SELECTIONPractice of having a standard or favorite pile type is NOT recommendedEach type has advantages & disadvantagesSeveral pile types or sections may meet the project design requirements
52 PILE SELECTIONTherefore, all candidate pile types should be carried forward in the design processFinal pile selection should be based on most economical section meeting the design requirements
53 Site Considerations on Pile Selection Remote areas may restrict equipment size.Local availability of pile materials and capabilities of local contractors.Waterborne operations may dictate use of shorter pile sections.Steep terrain may make use of certain pile equipment costly or impossible.Noise restrictions, vibration levels, or other environmental considerations may influence equipment selection and/or installation techniques.
54 Subsurface Effects on Pile Selection Typical ProblemRecommendationBoulders over Bearing StratumUse Heavy Low Displacement Pile With Shoe. Include Contingent Predrilling Item in Contract.Loose Cohesionless SoilUse Tapered Pile to Develop Maximum Shaft Resistance.Negative Shaft ResistanceAvoid Batter Piles. Use Smooth Steel Pile to Minimize Drag Load or Use Bitumen Coating or Plastic Wrap. Could Also Use Higher Design Stress.Deep Soft ClayUse Rough Concrete Piles to Increase Adhesion and Rate of Pore Water Dissipation.
55 Subsurface Effects on Pile Selection Typical ProblemRecommendationArtesian PressureHydrostatic Pressure May Cause Collapse of Mandrel Driven Shell Piles and Thin Wall Pipe. Pile Heave Common on Closed End Pipe.Adequate Pile Capacity Should be Developed Below Scour Depth (Design Load x SF). Tapered Pile Should Be Avoided Unless Taper Extends Below Scour Depth.ScourUse Prestressed Concrete Piles Where Hard Driving is Expected.Coarse Gravel Deposits
56 Pile Shape Effects on Pile Selection Shape CharacteristicPile TypesPlacement EffectsDisplacementClosed End Steel PipePrestressed ConcreteIncrease Lateral Ground Stress.Densify Cohesionless Soils.Temporarily Remolds and Weakens Cohesive Soils.Setup Time for Large Pile Groups in Sensitive Clays May Be Up To Six Months.
57 Pile Shape Effects on Pile Selection Shape CharacteristicPile TypesPlacement EffectsLow DisplacementSteel H-pileOpen End Steel PipeMinimal Disturbance to Soil.Not Recommended for Friction Piles in Coarse Granular Soils. Piles Often Have Low Driving Resistances in These Deposits Making Field Capacity Verification Difficult Resulting in Excessive Pile Lengths Installed.
58 Pile Shape Effects on Pile Selection Shape CharacteristicPile TypesPlacement EffectsTaperedTimberMonotubeTapertubeThin Wall ShellsIncreased Densification of Soil.High Capacity for Short Penetration Depth in Granular Soils.
59 Additional Information at www.piledrivers.org ? ? ?