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7/29/2019 Veloso Presentation
1/15
How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTED TECHNIQUES, A SOLUTION FOR ANCHORS
Veloso, Goncalo A. Geotechnical Engineer
Introduction
S.B.M.A. Technology
Post grouting Techniques and Design
Investigation Tests Results
Applications
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How to Enhance Ground Anchors Capacity in Soft Soils
When permanent anchorages are required on a retaining structure, the firstconcerns for the geotechnical engineer are the ground conditions and the
anchor achievable capacity
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How to Enhance Ground Anchors Capacity in Soft Soils
We design our anchors based on the existing ground properties, not thestrand capacity
S.B.M.A. Single Bore Multiple Anchor system
Can provide double the capacity of conventional anchors
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
As an alternative to conventional grouting techniques, anchors can be designedusing post grouting techniques, enabling the enhancement of the properties of
the soils and therefore increasing the capacity of the anchorages system
Grout up BoreholeGrout up BoreholeInsert anchor strands togetherInsert anchor strands together
with a post grouting pipe withwith a post grouting pipe with
manchetesmanchetes (TAM)(TAM)
4 8 HoursLater
Drill BoreholeDrill Borehole
Post GroutingPost Grouting
11stst StageStagePost GroutingPost Grouting
22ndnd StageStage
4 8 HoursLaterRepeat if
required
7 days after
PrePre--stressstress
ConclusionConclusion
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
The design of a ground anchor in cohesive soils is done using the followingequation (Littlejohn, 1970) :
CuLDTf xxxx =
lengthfixedoverstrengthshearundrainedAverage-
factorAdhesion-
lengthanchorFixed-
DiameterBorehole-
LoadWorking-
Cu
L
D
Tf
0.45=This means that with conventional grouting techniques in cohesive soils,less than half the clays undrained shear strength is mobilized in tension.
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
The design of a ground anchor in cohesive soils is done using the followingequation (Littlejohn, 1970) :
CuLDTf xxxx =
341 to.=
This means that with post grouting techniques in cohesive soils, we canenhance the working capacity of anchors up to 3 times or more aconventionally grouted anchor.
After post groutingAfter post grouting
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
Post Grouting effect:
7/29/2019 Veloso Presentation
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
Post Grouting effect:
Enlarged fixed length diameter by post grouting
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
Post Grouting effect:
Post Grouted fissures in stiff Clay
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
Post Grouting effect:
Section of exhumed post grouted anchor
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How to Enhance Ground Anchors Capacity in Soft Soils
POST GROUTING TECHNIQUES AND DESIGN
Post Grouting effect:
Section of exhumed post grouted anchor
BoreholeBorehole DiamDiam = 150mm= 150mm
Max.Max. DiamDiam. After post. After post
grouting = 210mmgrouting = 210mm
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How to Enhance Ground Anchors Capacity in Soft Soils
INVESTIGATION TESTS RESULTS
Earlier this year were carried out investigation tests, to determine the
behaviour of post grouted S.B.M.A. anchors compared to conventionallygrouted S.B.M.A.s and determine the enhancement achieved by the use ofthese techniques.
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How to Enhance Ground Anchors Capacity in Soft Soils
INVESTIGATION TESTS RESULTS
The results exceeded our expectations and the following results were
obtained:
For conventionally grouted S.B.M.A anchors
Average bond stress mobilized:
Up to 150 kN/m2
For Post grouted S.B.M.A. anchors
Average bond stress mobilized:
up to 450 kN/m2
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How to Enhance Ground Anchors Capacity in Soft Soils
APPLICATIONS
-Installation of anchors in poor ground conditions
-Reduce the number of anchors on a project by proposing to the clienthigher loads and larger spacing between anchors
-Reduce the overall length of the anchor when space restrictions exist
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How to Enhance Ground Anchors Capacity in Soft Soils
THANK YOU FOR YOUR TIME
WWW.KELLER-GE.CO.UK
WWW.SBMASYSTEMS.COM
WWW.THEANCHORMAN.COM
http://www.keller-ge.co.uk/http://www.sbmasystems.com/http://www.theanchorman.com/http://www.theanchorman.com/http://www.sbmasystems.com/http://www.keller-ge.co.uk/