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No Cell Phones, Please.No Cell Phones, Please.
Thank You.Thank You.
Division of Layne Christensen Company
Specialty Foundation ConstructionSpecialty Foundation Construction
Jet GroutingJet GroutingDrilled MicropilesDrilled MicropilesVibratory Ground Improvement & Stone ColumnsVibratory Ground Improvement & Stone ColumnsConstruction Drilling, Grouting & AnchorsConstruction Drilling, Grouting & Anchors
Central Artery / Tunnel ProjectCentral Artery / Tunnel ProjectContract C09C1Contract C09C1
US Interstate 90 & Interstate 93 InterchangeUS Interstate 90 & Interstate 93 InterchangeBoston, MassachusettsBoston, Massachusetts
Presented By: Pier Luigi Iovino, Division PresidentPresented By: Pier Luigi Iovino, Division President
APPLICATIONS…APPLICATIONS…
Temporary ConditionTemporary Condition Underpinning support of an abutment 22 drilled micropiles installed
Permanent Foundation SupportPermanent Foundation Support Support for new bridge foundation 90 drilled micropiles installed
Design ApplicationsDesign Applications
INSTALLATION TECHNIQUES…INSTALLATION TECHNIQUES…
Drilled micropiles were steel reinforced and cement grouted with a minimum rock socket diameter of 8-inches.
Rotary drilling technique utilized, with a permanent 5.5-inch O.D. steel casing connected to a 7-7/8-inch O.D. drill bit.
Design ApplicationsDesign Applications
Design ApplicationsDesign Applications
SIGNIFICANCE…SIGNIFICANCE…
Central Artery/Tunnel (CA/T) project is funded through the US Federal Highway Administration (FHWA).
Drilled micropiles are newly accepted method in US.
Drilled micropiles used as permanent bridge foundation component for FHWA funded project.
de facto acceptance of drilled micropiles as viable solution.
Design ConsiderationsDesign Considerations
THREE COMPONENTS…THREE COMPONENTS…
Threaded casing test results tension; compression and bending
Structural / Seismic
Geotechnical
Temporary ConditionTemporary Condition
Temporary ConditionTemporary Condition
STRUCTURAL CONSIDERATIONS…STRUCTURAL CONSIDERATIONS…
Pile Capacity = 67 tons / 134 kips.
Pile Diameter = 8 inches
Allowable design compressive stress of grout = 4,000 x 0.33 psi.
Temporary ConditionTemporary Condition
GEOTECHNICAL CONSIDERATIONS…GEOTECHNICAL CONSIDERATIONS…
Bearing stratum in bedrock.
Allowable friction stress in bedrock = 45 psi. Length of rock socket =
134 x 1000/(8 x 3.14 x 45 x 12) = 9.87 feet
Pile lengths to be 100 to 135 feet with 10 feet into bedrock.
Installation of Drilled MicropilesInstallation of Drilled Micropilesfor Temporary Underpinning of Abutmentfor Temporary Underpinning of Abutment
Drilled piles were installed in low headroom as part of a value Drilled piles were installed in low headroom as part of a value engineered proposal replacing contract design of driven piles. engineered proposal replacing contract design of driven piles.
Permanent Foundation SupportPermanent Foundation Support
Permanent Foundation SupportPermanent Foundation Support
STRUCTURAL CONSIDERATIONS…STRUCTURAL CONSIDERATIONS…
Pile Capacity = 100 tons / 80 kips. Pile Lateral Capacity = 2 kips.
Pile Diameter = 9 inches. Steel pipe to be 7 inches diameter, O.D. t=0.5” N-80
steel. Allowable design compressive stress of grout =
4,000 x 0.33 psi.
Permanent Foundation SupportPermanent Foundation Support
GEOTECHNICAL CONSIDERATIONS…GEOTECHNICAL CONSIDERATIONS…
Bearing stratum in bedrock.
Pile to be minimum 12 feet into bedrock. Skin friction area =
9 x 3.14 x 12 x 12 = 4069.4 sq. in.
Rock/grout friction stress = 200 x 1000/4069.4 = 49.1 psi
Pile Load Test FramePile Load Test Frame
Pile Load Test FramePile Load Test Frame
Installation of Drilled MicropilesInstallation of Drilled Micropilesfor Permanent Bridge Foundation Supportfor Permanent Bridge Foundation Support
Experienced. Equipped. Committed.Experienced. Equipped. Committed.
Boston • Richmond • Salt Lake City • Los Angeles • SeattleBoston • Richmond • Salt Lake City • Los Angeles • Seattle
Pittsburgh Pittsburgh • Hawaii • Puerto Rico • Italy• Hawaii • Puerto Rico • Italy
www.laynechristensen.com • 888-79-LAYNEwww.laynechristensen.com • 888-79-LAYNE
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