geosynthetics tencate geosynthetics...high tensile strength at low elongation. mobilization of high...

1

TenCate Geosynthetics

Geosynthetics Design and Specification in Cold Weather Environments

TenCate is the global leader in geosynthetics. We develop and produce materials that increase performance, reduce costs and enable people to achieve what was once unachievable. Our goal is to contribute significantly to progress in the industries in which we work.

TenCate Geosynthetics make the difference.GeosyntheticsIndustrial FabricsGrass

Protective & Outdoor FabricsAerospace CompositesArmor Composites

TenCate Mirafi®

3000 BCSplit-log “corduroy” roads over peat bogs

Road builders used straw, logs, and animal hides to stabilize weak subgrades

1926South Carolina Highway Dept -Cotton Fabric for Pavement Reinforcement

History of Geosynthetics

1950’s

New science emerged to produce textile products from synthetic plastics

Change from organic textiles to plastic textiles begins in carpet backing industry

1957Nico ter Kuile & Sons (Netherlands) produce first nylon sand bags for a hydraulic engineering project

1966Ten Cate Nicolon USA founded by Royal Ten Cate (Netherlands)

Experimental line of civil engineering fabrics is developed by Celanese(USA)

Fabrics are formed from“MIRA-cle FI-bers” = Mirafi

2

1970sConstruction of the national infrastructure and interstate system in United States provides a new market for the textile industry.

Market is established with a total of 3 million square yards installed in 1970.

1980sTen Cate Nicolon establishes its presence in the US in Cornelia, Georgia

Design procedures completed for roads, reinforced soil structures, embankments

1990sNicolon and Mirafi join forces

Explosive growth of geosynthetic products and applications

Nicolon Mirafi Group repositions itself in the global marketplaceas Mirafi® Construction Products

2000sTotal geosynthetic sales reach over 700 million square yards in the US

… 2000sTenCate Mirafi®

geosynthetics used successfully worldwide

Vast array of products available for numerous applications

Functions of Geosynthetics for Road Construction

–Separation

–Reinforcement

–Confinement

–Filtration

–Drainage

Roadway Stabilization & Reinforcement

Geosynthetic Reinforcement

“Use of a geosynthetic to aid in support of traffic loads, where loads may be vehicular loads over the life of the pavement, or construction equipment loads on the unpaved base course or subbase during construction.”

From Geosynthetics Manufacturer’s Assoc. (GMA) White Paper II

http://www.gmanow.com

3

Geosynthetic Functions –Roadway Stabilization & Reinforcement

• Separation• Confinement• Reinforcement• Filtration• Drainage

SeparationGeotextile placed between dissimilar materials so that the integrity of both can remain intact or be improved.

Old adage - “10 lbs. of stone placed on 10 lbs. of mud = 20 lbs. mud”

Confinement

Geosynthetic improvement of the ability to resist lateral movement of the aggregate

ReinforcementImprovement of the system strength created by the introduction of a geosynthetic into a soil/aggregate system

Filtration/Drainage

Fabric to soil systemthat allows for freeliquid flow (but no soil loss) across or through the planeof the fabric over an indefinitelylong period of time.

Geosynthetic Reinforcement Mechanisms

I. Lateral Restraint

II. Bearing Capacity Increase

III. Tension Membrane Support

4

I. Lateral RestraintRestraint of the lateral movement of base, or subbase, aggregate (confinement) through friction or interlock

Increase in modulus of base aggregate due to confinement

Improved vertical stress distribution on subgrade due to increased base modulus

Reduced shear strain along the top of the subgrade

(From GMA White Paper II ) Lateral Restraint

II. Bearing Capacity Increase

By forcing the potential bearing capacity failure surface to develop along alternate, higher shear strength surfaces.

(From GMA White Paper II )

Bearing Capacity Increase

III. Tensile Membrane Support

Mechanism mobilized under high deformation conditions.

(From GMA White Paper II ) Tension MembraneSupport

5

Geosynthetic Reinforcement Applications

• Base Reinforcement

• Subgrade Restraint (Stabilization)

Base Reinforcement

“…results from the addition of a geosynthetic at the bottom or within a base course to increase the structural or load-carrying capacity of a pavement system…to

1. improve the service life and/or2. obtain equivalent performance

with a reduced structural section.”

Subgrade:Controlled moisture content.

Conditions:CBR > 3Base Course Thickness < 250 mm (10”)

GeogridGeogrid

Base Reinforcement

Subgrade:Soils containing fines and occasionally wet.

Conditions:CBR > 3Base Course Thickness > 250 mm (10”)

GeotextileGeotextile

Base Reinforcement

Subgrade:Saturated, fine soils.

Conditions:CBR < 3Base Course Thickness > 250 mm (10”)

Geotextile

Base Reinforcement

GeogridGeogrid

Base Reinforcement BenefitsGeosynthetic placed as a tensile element at the bottom of or within a base / subbase aggregate

Improves service life

Obtains equivalent performance with reduced section

Reduces undercut, disturbance of subgrade

Reduces aggregate required for stabilization

6

Subgrade Restraint

“..may occur when a geosynthetic is placed at the subgrade / subbase or subgrade/base interface to increase the support of construction equipment over a weak or low subgrade …is the reinforcing component of stabilization…” Subgrade:

Fully saturated. Could be soil or liquid

Conditions:CBR < 3

Geotextile

Subgrade Restraint

Subgrade Restraint BenefitsGeosynthetic placed as a tensile element at the bottom of a base or subbase aggregate

Improves service life

Obtains equivalent performance with reduced section

Reduces undercut, disturbance of subgrade

Reduced aggregate required for stabilization

Provides access & constructability over very soft soils

Helps to establish a well-compacted, non-yielding platform -uniform support

Designing with Geosynthetics in Roadways

• Unpaved Road Applications

• Flexible Pavement Applications

• Rigid Pavement Applications

Unpaved Road Applications

• LARGE Deformations at Surface and Subgrade

• Very Soft Subgrade Conditions (CBR <1) can Require Bearing Capacity Analysis of Geosynthetic Reinforced System

• Very Heavy Loads on Moderate Strength Subgrade Conditions (CBR >1, <4) can also Require a Bearing Capacity Analysis of System

• NOT the Same as Flexible or Rigid Pavement Design

Unpaved Road Applications

References:• Barenberg and Bender, “Design and Behavior of Soil-Fabric-

Aggregate Systems,” 57th TRB, 1978• Giroud and Noiray, “Design of Geotextile Reinforced

Unpaved Roads,” ASCE, 1981• Hausmann, “Fabric Unpaved Road Design Methods –

Parametric Studies,” IFAI, 1986• Holtz and Sivakugan, “”Design Charts for Roads with

Geotextiles,” Geotex & Geomem, 1987

7

Flexible Pavement Applications

• SMALL Deformations at Surface and Subgrade (≤ 1”)

• Tensile Modulus of Geosynthetic at Low Strain Levels

• Interaction Between Geosynthetic and System Layers

• Benefit of Geosynthetic Accounted for in Different Ways in Different Design Methods

• Subgrade Soil Type (SM or CH) has a Significant Effect

• NOT the Same as Unpaved or Rigid Pavement Design

Flexible Pavement ApplicationsMethod 1a:• AASHTO Structural Number Calculation

• Assumes Immediate Benefit Provided to the Layer Directly Above Installed Geosynthetic

• Usually the Softer the Subgrade, The Larger the Benefit (i.e. more tensile strength of geosynthetic utilized)

• Modification (M) Values Typically Range from 1.1 to 1.5

• Provides Increased SN or Reduction of Layer Thickness for Equivalent SN


Method 1b:

• AASHTO Equivalent Single Axle Load (ESAL) Calculation Comparison

• Compare the Performance of Pavement Sections that Include Both Geosynthetic and Control Test Sections

• End Result is an Increase in the Number of ESAL Applications Due to Performance of Geosynthetic

• Traffic Benefit Ratio (TBR) Values Typically Range from Two to Four (Higher Numbers Unconservative)


Method 2:

• Layered Elastic Theory

• Computer Programs: CHEV, DAMA, BISAR, ELSYM5, SAPIV, ILLI-Pave, MICH-Pave, VESYS, KENLAYER…

• Use Visco-Elastic, Elastic and Plastic Material Layers

• Some Provide for Dynamic Loading Conditions

• Some Provide Damage Response from Accumulated Vehicle Loads


Method 2: Layered Elastic Theory• Provides Very Good to Excellent Analysis Results but

User Dependant• Can be Difficult to Incorporate Geosynthetic into

Analysis• Problem: Rigid Inclusion in Elastic Medium• Solution: Increase Modulus of Base Course to Reflect

Contribution of Geosynthetic


Method 2: Layered Elastic Theory

• Modulus Increase Can Vary from 50% to More than 200% Depending on CBR, Applied Load, Allowable Deformation/Deflection & Geosynthetic

• Very Good Correlation Between TRI’s Confinement Test (developed with TX DOT) and KENLAYER LET Analyses.

8


Method 3:• Mechanistic – Empirical Pavement Design• Finite Element/Difference Methods are the Mechanistic

Part of the Design Process• “Hey! This Test Section only Rutted This Much!” is the

Empirical (Anecdotal) Part of Design• Combined Process is the Most Accurate to Date• AASHTO 2000 (2006) is M-E Design Method


Method 3: M-E Design• FEM or FD Analyses can be Very Complex with

Thousands of Nodes/Elements.• Materials/Layers can be Very Complex: Linear,

Nonlinear, Elastic, Plastic, Visco Elastic…• All Add-up to Serious Computer Power and Time• Well Beyond the Scope of Most Pavement Designs


Method 3: M-E Design

• AASHTO 2006 Will Attempt to Incorporate a Geosynthetic Module

• Some Universities Have Developed Fairly Accurate Models and Methods

• Some States Have Developed “Beta” Computer Programs Incorporating M-E and Geosynthetics

• Currently the “Leading Edge” of Pavement Design Methods

Rigid Pavement Applications

• Filtration and Drainage are Main Applications

• Prevent Fines Loss at Joints When Dynamic Loads Create Differential Stresses in Saturated Subgrade Soils

• Can Use Unpaved Road Design Methods for Stabilizing/Reinforcing Subgrade Before Placing Concrete Slabs

• Using Correct Geosynthetic Should Still Increase Pavement Performance and Service Life

Other Pavement Considerations

• The Most Overlooked Feature Subgrade Soil(s) is Their Saturated Behavior

• Saturated Low-Plasticity Cohesive and Fine Non-Cohesive Soils Have the Potential to Disperse or Pipe under Dynamic Loads as Pore Pressures Exceed Soil Shear Strength

• Often Considered Suitable Subgrade Soils for Construction (until they get saturated)

• Separation is KEY for These Soils (Geotextile)


• High-Plasticity Cohesive Soils often Swell When Saturated (inevitable)

• Geosynthetics can Confine these Soils, Minimizing/Eliminating Differential Swell Potential

• Both Geogrids and Geotextiles Appear to Function Well in This Application

• Geotextiles offer Additional Long-Term Separation, Filtration and Drainage Functions

9


• CL, CH, ML,MH, Fine-Grained SM/SP are all Susceptible to Frost Heave in Cold Climates in Winter and Subsequent Frost Boil in Spring

• Nonwoven Geotextiles Provide a Capillary Break when Installed in the Vadose Zone

• Geosynthetics can also Confine these Soils, Minimizing or Eliminating Differential Swell Potential (and Frost Jacking)

• Geotextiles Appear to Function Best in This Application by offering Additional Separation, Filtration and Drainage Functions

TenCate Mirafi®Geosynthetics

Mirafi® HP geotextile

Mirafi® BXG biaxial geogrid

Mirafi® PEC geocomposite

Thermal and Moisture Effects

Temperature and moisture changes cause reflective cracking by vertical and or horizontal movement.

Climatic maps are used to assist in design considerations.

Thermal and Moisture Effects

Severe pavement conditions exist in areas III and VI that warrant special consideration for asphalt pavement overlays

Pavement Restoration ApplicationsThermal ApplicationsThermal Induced Block Cracking

Treated with fabric/asphalt tack and overlay

Pavement Restoration ApplicationsThermal ApplicationsTransverse-Longitudinal Joints Cracking

Treatment: Leveling course, fabric/tack and overlay

10

Pavement Restoration ApplicationsThermal Applications

Treatment:Leveling course with MPV700 6oz/sy paving fabric using modified asphalt tack and 2” overlay

Thermal Degradation & Age

Benefits of Paving Fabrics

Moisture Barrier

Reduces Crack Reflection

Offers Stress Relief

Increased Fatigue Life

Increased Pavement Bond

Reflection Cracking Over Time

0%10%20%30%40%50%60%70%80%

1 2 3 4 5 6 7 8

Time in Years After Overlay

% R

efle

ctiv

e C

rack

ing

1-1/4 AC Control 1-1/4 AC W Fabric

2-1/2" AC

Texas Study

Comparison of reflective cracks in 1.25” and 2.5”asphalt overlay verses 1.25” with paving fabric

TRB, January 1989

Reduces Reflection Cracking Increases Asphalt Overlay Life Expectancy

0

20

40

60

80

100

1 3 5 8 10 13 15 17 20

Years of ServicePa

vem

entC

ondi

tion

Inde

x

With Paving FabricWithout Paving Fabric

Pavement Condition Index

Serviceability & performance measured by pavement evaluation methods

Mirafi® PEC-Series Geocomposite

Mirafi PEC geocomposite

• High strength composite reinforcing geotextile

comprising non woven geotextile and high tenacity

polyester fibers.• Suitable for reinforcement of granular and

fine grained (cohesive) soils• Friction induced tensile strength• Facilitates drainage of pore water• Low creep behavior for long term structural

stability and more economical design.

11

Benefits

High tensile strengthat low elongation.Mobilization of high strength at low strain.Specially suited to the reinforcement of fine grained soils (sandy clay).

High resistance toconstruction stress.The nonwoven component protectsthe reinforcing yarnsagainst constructiondamage.

Mirafi PEC geocomposite

High in-plane drainagecapability. Allows dissipationof pore water pressurethrough geotextile andtherefore increasessoil strength characteristics andsoil/geotextile interfacefriction.

Back to MSE Navigation Slide

See your Mirafi representative, or contact us:888-795-0808 or www.mirafi.com

QUESTIONS?

geosynthetics tencate geosynthetics...high tensile strength at low elongation. mobilization of high...

Documents