Geotextiles May 2019 Agenda Overview Classification Polymers - - PDF document

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Fiji Technical Workshop

Geotextiles

May 2019

Agenda

• Overview
• Classification
• Polymers
• Stress Strain
• Design
• Specification

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Overview - Why do we need them? Overview - Why do we need them?

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Overview - Why do we need them? Classification

» Nonwoven

• Continuous Filament
• Needle punched
• Heat bonded
• Staple Fibre
• Needle punched
• Needle punched & Heat set

» Woven

• Slit Film
• Flat
• Fibrillated
• Multi-filament
• Mono-filament

» Knitted

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Polymers

» Polyester

• Bidim
• Texcel R

» Polypropylene

• Texcel P
• Polyfelt TS
• Mirafi N

Short term strength Long term strength

Polymers

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Stress/Strain Behavior

W : Woven CNW-HB : Continuous Filament Non Woven – Heat Bonded CNW-NP : Continuous Filament Non Woven – Needle Punched SNW-NP : Staple Fibre Non Woven – Needle Punched

Design – By Function

» Filtration

• Pore Size
• Through Flow
• Permeability
• Abrasion resistance
• CBR Burst
• Grab Strength
• Tear Strength

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Design – By Function

» Separation

• Tensile Strength
• Trapezoidal tear
• CBR Burst

Design – By Function

» Drainage

• Through flow
• Permeability
• Pore size

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Design – By Function

» Liner Protection

• Mass
• Density
• Fibre thickness
• CBR Burst

Design - Importance of Separation

» Loss of aggregate

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Design - Importance of Separation

0% 20% 40% 60% 80% 100% 0.0% 2.5% 5.0% 7.5% 10.0% 12.5% 15.0% 17.5% 20.0% 22.5% Pavement Load Carrying Capacity (%) of Original Design: AASHTO 1993 Flexible Pavement Design Method Aggregate Base Course Loss over Time (%)

Reduction in Flexible Pavement Load Carrying Capacity Due to the Loss of Aggregate Base Course (%) over Time

» Pavement performance

Design - Importance of Separation

» Full scale fields trials using different geogrids and geotextiles

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Design - Importance of Separation

» Pavement performance

Intermixing of granular layer with soft subgrade SOFT SUBGRADE Nonwoven Geotextile maintains the boundaries geotextile between adjacent soil layers SOFT SUBGRADE

Design - Properties

» Drainage

• Geotextile permeability 10 times subgrade

» Filtration

• Geotextile must retain subgrade material
• d50 < Geotextile pore size < d90

» Survivability

• Geotextile must not be damaged during

installation to such an extent that points above are rendered irrelevant

• Geotextile life must exceed design life

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Design - Cover material

Never overestimate the products’ ability to withstand mechanical impact!

» Size/Weight

• Greater mass = greater damage potential

» Drop Height

• Greater height = greater damage potential

» Angularity

• Sharp stone = greater damage potential

» Depth of cover

• Thin = greater damage potential

Design - Foundation

» Density

• Soft = geotextile bursting (CBR)
• Hard = geotextile splitting (Grab)

» Presence of Stones

• Stones are likely to increase damage due to

pinching/cutting (Mass)

» Slope

• Steeper = greater force on geotextile (Tear or

Tensile strength)

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Design – Field Trials

» Construction methodology

• Conduct field trials for site specific design

to eliminate uncertainty.

• Consider the following:
• Different drop heights i.e. 1.5 & 3m
• Excavator tracking

Design – Full Scale Testing

» Research & Development

• Conduct full scale rock drop tests
• Consider the following:
• Different drop heights i.e. 0.5, 1.0, 1.5 & 2.0m
• Different rock mass i.e. 250, 500 & 1000kg

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Design – Full Scale Testing

» Research & Development

• Develop Design curves

Design - When things go wrong

» Construction

• Despite extensive testing the construction

methodology was changed

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Design - When things go wrong

» Construction

• Use of a non specified woven geotextile

Specification

» Methods for specifying geotextiles

Past Experience Trial and Error Independent Technical Publications Suppliers - Guidelines

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» Parsons Brinckerhoff Independent Report – 2010

• The variation in test results was found to be significant, with one product failing to meet

the typical published data by 76%

• Typical data does not give an accurate platform on which to base engineering design
• In some instances weaker direction results were not presented
• Design certainty can be achieved through the use of MARVs presented in both the

machine and cross machine direction

Specification Regulatory Body Specifications

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Independent Specification

» Mechanical Properties

• AS 2001.2.3 Grab Tensile Strength

Independent Specification

» Mechanical Properties

• AS 3706.3 Trapezoidal Tear Strength

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Independent Specification

» Mechanical Properties

• AS 3706.4 CBR Puncture

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Independent Specification

» Mechanical Properties

• AS 3706.5 Drop Cone Impact (h )

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Independent Specification

» Hydraulic Properties

• AS 3706.9 Flow Rate and Permittivity

Blinding Clogging Filtration

Independent Specification

» Hydraulic Properties

• AS 3706.7 EOS (Dry Sieving) - O95

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Independent Specification

» Geotextile Application Categories

Application Material Requirement Filtration Class G1: Separation under / within Embankments Strength requirement in Table 2 & Table 6 Class 4 G2: Filtration/Separation under Embankments inc. Drainage Blankets Strength requirement in Table 2 & Table 6 Class 2 G3: Trench Drains / Highway Edge Drains Strength requirement in Table 3 & Table 6 Class 1 G4: Drainage/Separation Retaining Structures Strength requirement in Table 4 & Table 6 Class 1 G5: Under Rock Armour Revetment layer in Embankments Strength requirement for Class D and E in Table 6 Class 3 The use of geosynthetic material between two dissimilar materials to prevent the intermixing of materials Soft subgrade

Independent Specification

» Geotextile Application Separation

Granular layer

Geotextile separator

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Aggregate drainage blanket Embankment fill

Independent Specification

» Geotextile Application Separation

Geotextile separator

Soft subgrade

Independent Specification

» Selection of Geotextiles for Mechanical Separation (Table 2)

Nominal Max Stone Particle Size D (mm) Geotextile Strength Class 1 ≤ CBR ≤ 3 CBR > 3 ≤ 37.5 C (A29) A (A14) ≤ 75 C (A29) B (A19) ≤ 200 D (A39) C (A29) ≤ 400 E (A49) D (A39) ≤ 600 n/a E (A49)

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Geotextile Trench Depth < 3m

Independent Specification

» Geotextile Application Trench Drains

Independent Specification

»Selection of Geotextiles for Trench Drain (Table 5)

Nominal Max Stone Particle Size D (mm) Geotextile Strength Class Trench Depth <2m Trench Depth <3m ≤ 37.5 A (A14) B (A19) ≤ 75 B(A19) C (A29) ≤ 200 C (A29) D (A39)

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Geotextile Gabion Retaining Wall Reno Mattress

Independent Specification

» Geotextile Application Gabion walls / Mattresses

Independent Specification

» Selection of Geotextiles for Gabion Walls and Mattresses (Table 6)

Type of Structure Geotextile Strength Class Conventional concrete retaining walls Segmental block walls Reinforced soil panel walls B (A19) Gabion walls Crib walls Rock filled mattresses C (A29)

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Independent Specification

» Geotextile Application Rock Armour Revetments/Breakwaters

Geotextile Rock armour

Independent Specification

» Selection of Geotextiles under Rock Armour (See Table 7)

Nominal Max. Stone Particle Size D85 (mm) Geotextile Strength Class <200 D (A39) <400 E (A49)

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Independent Specification

» Independent Specification Example – TNZ F7

Independent Specification

» Independent Specification Example – TNZ F7

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Independent Specification Specification

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Questions?