Micro-trench reinstatement - NextGen Events Harper.pdf · Micro-Trench Reinstatement Techniques safetrack ® Successful Safetrack Microtrench Installations South Wales – Safetrack

Micro-Trench Reinstatement Techniques

www.stirlinglloyd.com

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�You�re not putting that in my road�

Micro-trench reinstatement

Presented By: Mike Harper – Development Director, Stirling Lloyd.

NextGen 12 - London



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Micro-trenching Reinstatement

•  What is the problem?

•  Why Micro-trench?

•  Limitations of traditional

reinstatement

•  Incorrect approaches

•  What�s required?

•  The Safetrack approach

•  Step by step examples



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•  Micro trenching not covered by the new �yellow book�

•  Little existing knowledge on how to reinstate micro trenches

•  Councils object on grounds of •  You�re cutting my road in half

•  No specification

•  Water ingress into the road

•  No HAPAS approval

•  Can�t compact asphalt in a slot

What is the problem?



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Why Microtrench? 1 - It�s Much Faster

!  4 to 5x faster than open trench

!  600 ln m per day on a trunk route (achieved in Shetland)

!  Less disruption to the public

!  Less traffic congestion

Getting FTTP to 90% of UK addresses could mean 247,500 km of fibre installation!



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Why Microtrench?

2 - Lower Environmental Impact

!  Significantly less waste created to be disposed of

!  Less new materials imported

!  Fewer truck movements because of the above

!  Less traffic congestion because of fast turnaround

!  All this means lower CO2



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Why Microtrench? 3 - Lower Cost

!  Lower costs because of speed / waste & new material

!  Lower long term maintenance costs if you get the reinstatement right (no secondary compaction / sunken trenches)

!  Less damage to the highway asset (shallower – less impact on sub-base / surface course and services)



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•  Traditional reinstatement materials (macadam & asphalt) were not designed for this.

•  Can�t place / compact hot asphalt / macadam in a 20mm wide slot

•  Pouring neat bitumen is not the solution (no strength or skid resistance)

•  Trying to tamp cold lay asphalt? Early failure due to lack of compaction

•  Most methods will let water into the pavement!!

What is the problem?



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1.  Cement grout to the surface Not flexible No bond to asphalt Cracking / water ingress Slow strength gain

2. Epoxy Mortar

Not flexible Long cure time = greater disruption Cracking / water ingress

2. Cold lay macadam

Needs adequate compaction to achieve cohesion Little bond to cut asphalt edges Ineffective seal – water ingress Lack of cohesion

Incorrect approaches and why?



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•  Most recent advice note from DCMS – the Department for Culture, Media & Sport - outlines current best practice

•  This can be complied with and is a good start

•  Key drawback is reinstatement in the asphalt layer only at depths that exceed the asphalt depth in evolved roads

What current advice is there?



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•  A fluid material that will penetrate - needs no compaction

•  High bond strength to the cut asphalt

•  Supports the cut edges of the asphalt

•  Compatible flexibility with asphalt

•  No shrinkage & waterproof seal

•  Skid resistance

•  Dimensional stability under traffic

•  Fast return to service

•  BBA / HAPAS approval

So what do we need to reinstate a micro-trench effectively?



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•  Materials designed for highway use

•  Safetrack is fluid & self compacting

•  Cold applied – safe to use

•  No �site mix� – Factory batched (QA)

•  Dimensional stability – can�t be �trafficked out�, rut or sink (no secondary compaction)

•  Bond strength > cohesive strength of asphalt (bonds the road back together)

•  Waterproof and seals the road

•  Skid resistant

•  No glare

•  BBA / HAPAS approved

The �Safetrack� approach



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Additional benefits

•  No specialist equipment = quality installation from every team, all the time.

•  No heating = no risks to public and operatives + less CO2.

•  Safetrack MTI indicator layer = reduces risk of accidental damage in future by using yellow below the surface

•  Doesn�t damage the fibre installation

•  Permits removal / reinstatement of duct if required.

The Safetrack approach



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Successful Safetrack Microtrench Installations

South Wales – Safetrack approved for use by the Welsh Assembly for microtrenching on trunk roads in 2009

Shetland – Safetrack products successfully used over last 3 years – now on Phase 4.

Galway – Safetrack products used over last 2 years – now in Phase 2.

Bournemouth – multiple products tried without success. Safetrack products were the only ones regarded successful by Bournemouth CC.



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Microtrenching

Step by step through the process



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Cutting

•  Cutting machine type is very important

•  Match the duct to the cut size

•  Avoid oversize cutting

•  20mm cut / 16mm duct is ideal where possible



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•  Dry cutting is a clean process - no slurry waste from wet cutting

•  Vacuum extraction �hoovers� dust from the slot

•  Cutting depth is constant (150mm here)

•  Overbreak along the cut is minimal

Cutting



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•  Vacuum extraction avoids dust

Cutting



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Cutting

•  Resultant cut is even width

•  Minimal damage to surrounding asphalt

•  Minimal work area

•  Fast, clean and accurate



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Drying

•  Safetrack drying lance removes any residual dust

•  Dries the cut asphalt faces using air and / or heat if required

•  A clean dry asphalt face = high bond strength and a good seal



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•  Protective foam strip into the bottom of the micro-trench

•  Microduct – with or without fibres – is installed

•  A protective foam strip is applied over the duct

•  The micro-trench is now ready to be permanently reinstated

Installation



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•  Installing Safetrack Crack Infill into the micro-trench

•  Cold process – simple and accurate placement

•  Can use yellow indicator below the surface to avoid future damage

•  BBA / HAPAS approved product

Reinstatement



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•  Yellow first pass up to 10mm from the surface

•  Black capping layer with embedded aggregate for skid resistance

Reinstatement



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•  Safetrack Overbanding black surface layer

•  Aggregate overscatter

Reinstatement



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•  Process train approach moves continuously along the road

•  All the processes are in this image

•  Rapid cure of the reinstatement means minimal traffic management behind the works

•  600 ln m per day complete installation

Reinstatement



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•  Completed micro-trench

•  Fibre duct installed at 150mm deep

•  Safetrack Overbanding permanent reinstatement

•  Up to 600 ln m per day completed and returned to service same day (Shetland rural roads)

Reinstatement



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•  Traditional trench dig would be 5x slower

•  Would create much more disruption for residents and road users

•  Uses far more material and creates much more waste

•  Far higher carbon footprint

•  Much greater damage to the road or pavement asset and likely requirements for more long term maintenance (secondary compaction etc)

•  We need micro-trenching but we need to do it right.

But we�ve always done it this way ……



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For more information contact us:

t: 01565 633111

m: 07976 517200

e: [email protected]

w: www.highwaymaintenanceproducts.co.uk

Questions?

Documents

Micro-trench reinstatement - NextGen Events Harper.pdf · Micro-Trench Reinstatement Techniques safetrack ® Successful Safetrack Microtrench Installations South Wales – Safetrack