use of geogrids in wexford · geosynthetic functions & examples separation drainage /...
TRANSCRIPT
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Use of Geogrids in Wexford
Donal McLoughlin BEng CEng
Wexford County Council
March 2019
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Aim
To give an insight, based on Wexford County Council’s experience, into some of the practical pavement applications of geogrids from a local authority point of view.
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Content
• Brief Overview of Geosynthetics• Main types used for road construction applications.
• Historical applications in WCC
• Case study • N25 Primary Road Overlay
• Site selection
• Design
• Works
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Types of Geosynthetics
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Geosynthetic Functions & Examples
SEPARATION
DRAINAGE / FILTRATION
ASPHALT REINFORCEMENT
REINFORCEMENT
REINFORCEMENT
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Unbound Sub-Base
Asphalt Base/Bearing course
Binder course
Asphalt Surface course New Construction
AdequateFormation
Poor Formation
Two main Types.
• Unbound Sub base reinforcement.
• Asphalt/ surface course reinforcement
Geogrids and Road Construction
Existing
Maintenance Strengthening
Subgrade Formation
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Geosynthetics for Sub-base Reinforcement
• Reduces deformations in the sub-base.
• Provides soil separation (With a backing Geotextile)
• Mitigation of settlements => extension of road service life.
• Reduces the need for large depths of construction.
Different Types of Reinforcement
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Geosynthetics for Asphalt Reinforcement.
• Retardation of reflection cracking.
• Extends rehabilitation intervals.
• Extends the service life of road.
• Economic solution to add strength to a road.
• Reduces maintenance costs.
Different Types of Reinforcement
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Typical Pavement Crack (Without Reinforcement)Dynamic Fatigue Tests
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Typical Pavement Crack (With Reinforcement)Dynamic Fatigue tests
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R702 Rehabilitation/ Water Main Rehabilitation
Wexford Co. Co. Experience
Sub-Base Reinforcement Application
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R730 Wexford Quay 2009 2019
Wexford Co. Co. Experience
Asphalt Reinforcement Application
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Case studyN25 Ballynabola to Raheenvarren
Pavement Scheme
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N25 Site Specific Information.
• National Primary Road
• Single Carriageway with hard shoulders
• AADT = 8000
• %HGV = 7.8
• Pavement Deteriorating (2014/2015)
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Existing Pavement Condition : Rutting in wheel Track
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Existing Pavement Condition : Cracking
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Existing Hard Shoulder Failure
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TII Pavement Management System
• TII Asset Management Survey (2015 Red Flag).Wheel track rutting CrackingLoss of skid resistance
• Identified the condition of the carriageway as Fair / Poor
• Local Authority survey work / interventions also backed up survey results.
• TII recommended that preliminary investigations be carried out, with a view to demonstrating the need for a proposed pavement scheme.
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Recommended Solution
• Main Carriageway
• Sectional repair of compromised pavement to a depth of 200mm
• Overlay existing pavement with 55mm Binder Course & 45mm HRA
• Install Asphalt Reinforcement to upper Layers to prevent future cracking
& extend the life of the pavement
• Hard Shoulder
• Cold mill Hard Shoulder to Sub-base level & install geo-composite
reinforcement (Geogrid + Geotextile)
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Cross Section
Asphalt Reinforcement Sub base reinforcement
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Reinforcement
• Sub-Base Reinforcement
• Reinforcement, filtration, separation (All in one)
• Easy to install
• Good resistance against installation damage
• Asphalt Reinforcement
• Flexible and easy to install
• Bitumen coated polyester (suitable for fine milled surface)
• Good resistance against installation damage
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Extent of the Works
• Total length of works 3.6 km
• Application of Asphalt Reinforcement over affected area
• Application of Unbound Reinforcement in Hard Shoulder
• Contract awarded to Roadstone Ltd.
• Contract value - €2 million.
Works Programme Summer 2017
1. Sectional repair of main carriageway
2. Excavate and repair WBHS. Including unbound reinforcement.
3. Pavement overlay Main Carriageway. Install Asphalt
reinforcement on affected sections.
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Hard shoulder Rehabilitation.
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Asphalt Reinforcement – Bond Coating
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Asphalt Reinforcement – Laying Process
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Main Carriageway
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Asphalt Reinforcement – Rolling
• Ultra light Weight nonwoven Backing• Tensile Strength 50 Kn/m• Bitumen content of Coating > 60%
Combination of bitumen coating grid & bond coat emulsion provided an extremely strong bond between the asphalt layers & geogrid
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Asphalt Reinforcement – Paving
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Today:
Completed Scheme
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Completed Scheme
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Completed Scheme
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Thank You
Donal Mcloughlin BEng CEng
Wexford County Council
March 2019