Drilled Shaft Foundations for the CR #85 Bridge · Main bridge contract $1,522,000 Prestressed box...

Anthony J. Anthony J. BorrelliBorrelli, PE Stephen C. , PE Stephen C. CathermanCatherman, PE, PEBergmann AssociatesBergmann Associates Steuben County DPWSteuben County DPW

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Drilled Shaft Foundations for the CR #85 BridgeDrilled Shaft Foundations for the CR #85 Bridge

Project Overview

Locally-Administered, Federal-Aid Project w/ NYSDOT Region 6

Owner: Steuben County Department of Public Works

Engineer: Bergmann Associates with:Tierney Geotechnical Engineering

SJB Drilling

Project Overview (continued)

Contractor: The L.C. Whitford Company

Box Beam Supplier: Schuylkill Products

Construction Costs:

Main bridge contract $1,522,000Prestressed box beams $164,000Temporary bridge $342,000Total cost $2,028,000

Site Overview

CR #85

NYS Rte 417

Tuscarora Creek Stats:121 sq mi drainage area18,000 cfs peak flow 14 fps max. velocity

Project Timeline

9/11/04 – Bridge closed, detour set up

Project Timeline

12/12/04 – Temporary bridge opens

Project Timeline

6/1/05 – Construction begins

Project Timeline

11/18/05 – New bridge opened

Shaft Foundation Challenges:Construction diligence and expertise Specialized equipment Engineering expertise

Shaft Foundation ChallengesShaft Foundation Challenges::Construction diligence and expertise Construction diligence and expertise Specialized equipment Specialized equipment Engineering expertiseEngineering expertise

Shaft Foundation Advantages:Minimized shaft cap footprint Adaptable to varying geologyHigh lateral / axial capacity

Shaft Foundation AdvantagesShaft Foundation Advantages::Minimized shaft cap footprint Minimized shaft cap footprint Adaptable to varying geologyAdaptable to varying geologyHigh lateral / axial capacityHigh lateral / axial capacity

Shaft Reinforcement

Rebar cages constructed on stands

Hinged-Gate Details

Shaft Concrete

Tremie tube

Validation of CSL ResultsCSL testing should not be sole basis for shaft rejection – false results can occur

Inspector reports & drill logs

Compressive strength tests

Additional test methods:

Angled CSL testCross-hole tomographyCoring

Defect Remediation Options

Refined analysis

Full scale load test

Abandon shaft & install new adjacent shaft

Install other adjacent foundation system

Structural grouting

Footing Construction1:1.5 Slope

Footing Construction

Footing Reinforcement

AbutmentConstruction

AbutmentConstruction

Box Beam Installation

Deck Placement

Finished Elevation

Completed Bridge

Before After

Lessons LearnedThe more subsurface information, the better

Specify a test shaft or installation sequence

Design with construction in mind

Careful contractor attention required for tremies

Engineer, inspector, contractor and owner must all understand shaft construction practices

Let the contractor select methods and equipment

Types of Shaft DefectsBulge or neck in shaft

Non-homogeneous section: Sand lensSidewall cave-inVoids (esp. outside rebar cage)Excessive waterForeign materials

“Soft Toe”

Over consolidation

Off-location / out-of-plumb

Correct flaws if present in >50% of the profiles

Correct defects if present in 2 or more profiles

False results:

Damaged / unbonded tubesGreen concreteTube alignment

Interpreting CSL Results

Quality Control Measures

Tight specification with proper tolerances

Thorough review of contractor submittals

Trial or technique shafts (not part of final structure)

Test shaft (production shaft)

Knowledgeable personnel

Proper concrete placement practices

Integrity testing