04-Ansari PPT.pdf

8/17/2019 04-Ansari PPT.pdf

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Slope Support Design & Performance

1Nadir Ansari & M. Janes, P.Eng.2

Slope Support and Design

Presentation Schedule:• Problem definition

• es gn osop y

• Outcomes:

• CN Grimsby

• Castlefield Lowe’s

• Whitemud Hwy

• Monitoring Program

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• Summary & Discussion


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Problem Definition

When is it Slope Support vs Shoring?

• When the slope is preserved long term

• New structures support the slope

• When the slope is reinforced

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Design Philosophy

1. Excellence in geotechnicalinvestigation and testing

2. Advanced analytical methods

1. Caveat – know the answer first

3. Design to the probable, not the

worst case

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4. Excellence in monitoring

5. Constant calibration


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Design Philosophy

“Large savings can often be made by designing on thebasis of the most probable rather than the mostunfavourable possibilities. The gaps in the availableinformation are filled by observations duringconstruction and the design is modified in accordancewith these findings.”

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Terzaghi and Peck


CN Grimsby

• uppor uns a e s ope

• Weak fills, uncompacted embankment

• Moving slope

• Maintain rail right of way

• Low impact to neighbours

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• Arrest slope movements


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CN Grimsby

• Non reticulated Micropile wall with cap

• Poor access

• No re-grading of slope allowed

• Low construction slope loading

• FEA analysis - FLAC

•

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• movement reduction

CN Grimsby

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CN Grimsby

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CN Grimsby

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FEA original condition: Slough and plastic failure x


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CN Grimsby

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Non reticulated Micropile wall with cap

CN Grimsby

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Non reticulated Micropile wall cap


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CN Grimsby

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Reduced movement & no plasticity


Whitemud Hwy Development

• uppor s ope – ex s ng s e,

• Maintain highway right of way

• Increase slope steepness 3:1 to 2:1

• Arrest slope movements

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Whitemud Original Slope

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Whitemud

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Whitemud

• Path to permanent was temporary

• Shotcrete support wall to allow:

• Caisson bench installation

• Integrating, cascading, ringed footings

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• CIP orses oe arcs a ove gra e

• Oops a weak layer !

Whitemud

Original condition with bin walls 3:1 slope

ro ec ca e or s eepen ng o : s ope

Final walls of integrated arcs

Proposed geometry

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Whitemud

Permanent wall incorporatedCIP inte rated arcs

Both footings and walls above

Caissons & Anchors thru weak zone

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Whitemud

20Construction underway


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Whitemud

21Injection anchor installation

Whitemud

Failure during construction

along weak clay seam plane - 25°

Remediation required early installation

of caissons and permanent anchors

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Whitemud

Inclinometer

Data

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layer at 8 m

depth

Whitemud

24Failure interrupts construction sequence


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Whitemud

25Forming of caisson supported step ring footing

Whitemud

26Completed arc structure prior to backfill


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Castlefield Lowe’s Development

• xcava e n o ex s ng s ope

• Aesthetic final slope treatment

• Large radii corner accommodates

truck turning radius

• Maintain tower & roadwa above

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• Increase overall slope steepness

Castlefield Lowe’s

28Site prior to excavation


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Plan of wall

within

constrained

area

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Classical Rankine analysis of loads

e eory:

Allowed ‘dissipation’ of load within shell

Supported load through:Skin friction between wall and soil,

Added anchor capacity as easement permitted

Sloped wall face

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Elevation of high constrained area


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Post tensioned shotcrete to control movement

Double layer:

Base 150 mm for strength

Overlay 100 mm thick coloured

shotcrete façade

Attention to drainage above and behind wall

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Wall onstruction Detail

Concern regardingfrost action

thickening of wall at

anchor head

Difficult detail to

attain in field with

draina e material

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Wall onstruction Detail

Top of wall detail: swale &

fence

: v

drainage panels & perimeter

toe drain

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onstructability

39Swale installation


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Monitoring:

. xce ence n mon or ng qua y

2. Best possible accuracy & precision

3. Timely results & reporting

4. Site & problem specific

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5. The proof is in the performance


Summary

• Client,Site,Problem specific solutions

• 3 problems - 3 solutions

• Attention to environmental effects

• Climate

• Corrosion

• Monitorin to establish & enhance

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performance as required


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Acknowledgements•

www.hcmatcon.ca

• Geo-Foundations Contractors

www.geofoundations.ca

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