Geocomposite Geocomposite Subsurface Drainage Subsurface Drainage

Systems Systems Presented by:

Developed by: Aigen Zhao, PhD, PETenax Corporation

VP/Engineering

CONTENTS OF CONTENTS OF PRESENTATIONPRESENTATION

Water in Pavement Systems Conventional Drainage Solutions Geocomposite Drainage Layer Solutions Drainage Requirements for Permeable

Layer Geocomposite Drainage Effectiveness Cost Benefits Case Histories

Related ReferencesRelated References

FHWA, 1992, Demonstration project 87: “Drainable pavement systems”, Participant Notebook, FHWA-SA-92-008.

US Army Corps of Engineers, 1992, “Engineering and design drainage layers for pavements”, Engineer Technical Letter, 1110-3-435, Department of Army.

Cedergren, 1987, “Drainage of highway and airfield pavements”, R. E. Krieger publishing Co, FL

Christopher and McGuffey, 1997, NCHRP Synthesis of highway practice 239, “Pavement subsurface drainage systems”, Transportation Research Board.

Christopher, Hayden, and Zhao, 1999, “Roadway Base and Subgrade Geocomposite Drainage Layers, “ ASTM STP 1390, American Society for Testing and Materials, June.

Christopher and Zhao, 2001, “Design manual for roadway geocomposite underdrain systems”, Tenax Corporation.

Standing water in a pavement indicates low permeability and poor drainage Standing water in a pavement indicates low permeability and poor drainage

Under traffic loading, water and base material squirting up through joint in Under traffic loading, water and base material squirting up through joint in PCC pavementPCC pavement

Water in Pavement SystemsWater in Pavement Systems

AASHTO (1993) reports: Water in the asphalt surface

Moisture damage, modulus reduction and loss of tensile strength Saturation reduces dry modulus of the asphalt 30 %

Moisture in unbound aggregate base and subbase Loss of stiffness 50 %

Water in asphalt-treated base Modulus reduction of up to 30 percent Increase erosion susceptibility of cement or lime treated bases

Saturated fine grained roadbed soil Modulus reductions 50 %

AASHTO Guide for Design of Pavement Structures, 1993

% of Time Structural Section is Saturated0 10 20 30 40 50

0

20

40

60

80

100S = Severity Factor

S=5

S=10

S=20

For a pavement section with a moderate severity factor of 10, if 10% of time the pavement is approaching saturation, the pavement service life could be reduced by half.

Ref. Cedergren, H.R. 1987, Drainage of highway and airfield pavements, Robert E Krieger Publishing Co, FL.

Severity factor Severity factor measures measures the relative the relative damage damage between wet between wet and dry periodsand dry periods

AASHTO Drainage AASHTO Drainage DefinitionsDefinitions

Quality of Drainage

Excellent

Good

Fair

Poor

Very Poor

Water Removed Within*

2 Hours

1 Day

1 Week

1 Month

Water will not Drain

AASHTO Guide for Design of Pavement Structures, 1993

*Based on time to drain

Design for Drainage Design for Drainage (AASHTO, 1993 Design Method)(AASHTO, 1993 Design Method)

Structural Number (SN) for a pavement section is:

SN = a1*d1 + a2*d2*m2 + a3*d3*m3

a1 a2 a3 = layer coefficients for AC, BC and Sub base layers

d1, d2, d3 = their thickness m2, m3 = drainage coefficients for the base and

sub base layer

Percent of Time Pavement Structure is Exposed to Moisture Levels

Approaching SaturationQuality of

Drainage Less than

1% 1-5% 5-25%

Greater than

25%

Excellent 1.25- 1.20 1.20-1.15 1.15-1.10 1.10

Good 1.20-1.15 1.15-1.10 1.10-1.00 1.00

Fair 1.15- 1.10 1.10-1.00 1.00-0.90 0.90

Poor 1.10-1.00 1.00-0.90 0.90-0.80 0.80

Very poor 1.00-0.90 0.90-0.80 0.80-0.70 0.70

Recommended Drainage Coefficient, cRecommended Drainage Coefficient, cd,d, for for

Rigid PavementsRigid Pavements

AASHTO Guide for Design of Pavement Structures, 1993

Recommended values for drainage modifier, mi, for Recommended values for drainage modifier, mi, for untreated base and subbase materials in flexible pavements untreated base and subbase materials in flexible pavements

(AASHTO, 1993).(AASHTO, 1993).

Quality of Drainage

Percent of time pavement is exposed to moisture levels approachingsaturation

Less than 1% 1 to 5% 5 to 25% More than 25%

Excellent 1.40-1.35 1.35-1.30 1.30-1.20 1.20

Good 1.35-1.25 1.25-1.15 1.15-1.00 1.00

Fair 1.25-1.15 1.15-1.05 1.00-0.80 0.80

Poor 1.15-1.05 1.05-0.80 0.80-0.60 0.60

Very Poor 1.05-0.95 0.95-0.75 0.75-0.40 0.40

Page. 6 Table 2 - from the Design Manual for Roadway Geocomposite Underdrain SystemsBy, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.

Christopher and McGuffey, 1997, NCHRP Synthesis 239, “Pavement subsurface drainage systems”

Components of a Drainable Components of a Drainable PavementPavement

Time to DrainTime to Drain

For two lane road - Lane width = 24 ft, Slope = 0.01

Base k time to drain Quality

OGB 1000 ft/day 2 hrs to drain Excellent

DGAB 1 ft/day 1 week Fair

DGAB w/ fines 0.1 ft/day 1 month Poor

Reality no drains does not drain Very Poor

“Although the benefits of well-drained pavements have been clearly shown, there has always been hesitancy on the part of practitioners to use open-graded base courses because of concerns regarding a lack of stability of the open-graded layer….

There is doubt as to how long the hydraulic conductivity of open-graded bases can be maintained because of upward migration of subgrade soil particles into the layer, as well as, possibly, the infiltration of fine particles from fractures in the pavement surface….”

TRB Committee A2K06 on Subsurface Drainage Research Proposal for NCHRP “STABILITY AND DRAINABILITY OF OPEN-GRADED BASE COURSES”

TRADEOFF OF STABILITY AND TRADEOFF OF STABILITY AND DRAINABILITY OF OGBCDRAINABILITY OF OGBC

A Tri-planar Drainage Geocomposite A Tri-planar Drainage Geocomposite Structure: RoaDrainStructure: RoaDrainTMTM

New Alternative Drainage Material:New Alternative Drainage Material:Geocomposite Drainage Layers Geocomposite Drainage Layers

Maine DOTMaine DOT

Uses of Horizontal Geocomposite Uses of Horizontal Geocomposite Drainage LayersDrainage Layers

Excellent Drainage Enhanced design life Energy absorbing to mitigate reflective

cracks from the existing PCC base Separation between new asphalt overlay

and subbase

Tri-Planar RoaDrain Geocomposite to Replace Drainable Tri-Planar RoaDrain Geocomposite to Replace Drainable Aggregate in Flexible Pavement SystemsAggregate in Flexible Pavement Systems

Asphalt PavementAsphalt Pavement

Drainage

For Rigid Pavements Excellent drainage

Improved Design

> Cd

Geocomposite to Replace Drainable Aggregate Geocomposite to Replace Drainable Aggregate in Rigid or Flexible Pavement Systemsin Rigid or Flexible Pavement Systems

Drainage - Improved Pavement Design > m or Cd

> SN Separation

Improved long term performance

Enhance Drainage of Dense Graded Enhance Drainage of Dense Graded Base by Shortening Drainage DistanceBase by Shortening Drainage Distance

Stabilization Improved construction

Reinforcement Improved Load Support

Geocomposite Drain RequirementsGeocomposite Drain Requirements

Sufficiently high inflow permeability to allow uninhibited flow from the adjacent pavement section during any major rainfall event

Sufficient stiffness to support traffic without significant deformation under dynamic loading

Sufficient transmissivity to rapidly drain the pavement section and prevent saturation of the base

Sufficient air void exist within the geocomposite to provide a capillary break

Christopher, Hayden, and Zhao, “Roadway Base and Subgrade Geocomposite Drainage Layers, “ ASTM STP 1390, American Society for Testing and Materials, June,1999.

RoaDrainRoaDrainTMTM – – Important PropertiesImportant Properties

High Transmissivity

Creep Resistance under High Loads Long-term Resistance to Compression

Stability Traffic Loads = Univ. of Illinois Study

A Void-Maintaining Structure

Geotextile Filtration Requirements

Fatigue Test Setup and Representative ResultsFatigue Test Setup and Representative Results(Univ. Of Il. Advanced Transportation Research and Engineering Lab)

Potential Cost - BenefitPotential Cost - Benefit

Quality of Drainage m

Structural Number

(maintaining section)

Reduction

in Base (maintaining asphalt thickness and SN =

4.3)

Reduction in

Asphalt (maintaining

base thickness and SN = 4.3)

Estimated

Performance Period

(maintaining section)*

Excellent (by using RoaDrainTM)

1.3

4.93

- 3.5 in.

-1.43 in.

38 yrs

Good Standard Design

1.0

4.3

0

0

20 yrs

Poor ? Reality for most designs

0.7

3.67

+6.5 in.

+1.43 in.

8 yrs

Total savings

-

-

10 in.

2.86 in.

Up to 30 yrs

* Based on 20-year performance period and a 3 percent growth

Comparison of drainage performance with and Comparison of drainage performance with and without RoaDrain geocomposite drainage net. without RoaDrain geocomposite drainage net.

Page. 21 Table 3 - from the Design Manual for Roadway Geocomposite Underdrain SystemsBy, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.

RoaDrain only Base drainage only RoaDrainunder base

Resultant slope 0.02 0.02 1

Resultant length 24 feet 24 1

Thickness 0.02 1 1

Effective porosity 0.69 0.15 0.15

Transmissivity 4500 1 1

Results

Slope factor: 24 0.48 1

M: 0.088 86 0.15

Time to drain (hours): 0.02 840 0.86

Equivalency of RoaDrain to 4” OGBL – flow Equivalency of RoaDrain to 4” OGBL – flow capacitycapacity

4”- OGBL with (k =1000 – 3000 ft/day) transmissivity = 300-1000 ft3/day/ft

Flow rate @2% = 6 – 20 ft3/day/ft

RoaDrain Synthetic Drainable Base Layer (SDBL) transmissivity = 1500 ft3/day/ft @15kpsf and 2% after considering an equivalency factor between geocomposite drain and soil drain.

Flow rate @2% = 30 ft3/day/ft

SDBL > OGBLSDBL > OGBL

Frost heave refers to the raising of a surface due to the formation of ice lenses in the underlying soil.

Frost Heave & RoaDrain as a Capillary Barrier

U.S. Army Corps of Engineers (1963):

1. Limit the amount of frost-susceptible soil subjected to freezing temperatures.

2. Design of adequate bearing capacity during the most critical climatic period a significant increase in aggregate thickness

Solutions to Reduce Frost DamageSolutions to Reduce Frost Damage

Pavement

Non-frost susceptible base

Frost penetration depth

No this kind of ice lens

Frost susceptible soilRoaDrain Capillary Barrier

Water table

Solutions to Reduce Frost Damage – Solutions to Reduce Frost Damage – RoaDrain Capillary BreakRoaDrain Capillary Break

•Capillary break must be placed between the ground water table and frost penetration depth

• In addition to capillary rise, water flow to the freezing front is caused by an up-moving gradient related to temperature and pressure changes

US Army Cold Regions Research and US Army Cold Regions Research and Engineering Lab (CRREL) Study ConcludedEngineering Lab (CRREL) Study Concluded::

RoaDrain was a very effective capillary barrier and eliminated frost heave in specimens from the Maine DOT test site

Freezing did not cause any observable physical changes

Henry and Affleck, “Freezing tests on lean clay with Tenax tri-planar geocomposite as capillary barrier”

Maine DOT Field StudyMaine DOT Field StudyFrankfort–Winterport Route 1A Frankfort–Winterport Route 1A

Drainage Test SectionsDrainage Test Sections

Geocomposite Pavement Geocomposite Pavement DrainsDrains

Construction DetailsConstruction DetailsPreparing Collection Pipe DitchPreparing Collection Pipe Ditch

Construction DetailsConstruction DetailsCollection Pipe Inlet/Outlet SystemCollection Pipe Inlet/Outlet System

Construction DetailsConstruction DetailsGeocomposite PlacementGeocomposite Placement

Plastic ties being secured

Seams sewn 4 man-hours

per 100’ of installation

Construction DetailsConstruction DetailsGeocomposite Placed Above Base Course cont.Geocomposite Placed Above Base Course cont.

Base course graded

Tack coat applied

Geocomposite placed

Pavement surface placed

Drainage DischargeDrainage Discharge

Drainage DischargeDrainage Discharge

RoaDrain – Good to Excellent DrainageRoaDrain – Good to Excellent Drainage

Discharge during the first year of monitoring corresponds strongly with precipitation events and water table levels. Based on the AASHTO definitions for pavement drainage capacity , the quality of drainage in the RoaDrain test section is good to excellent.

Falling Weight Deflectometer (FWD) ResultsFalling Weight Deflectometer (FWD) Results (Drainage Sections), Maine DOT (Drainage Sections), Maine DOT

0

1

2

3

4

5

6

7

8St

ruct

ural

Num

ber,

SN

(in

ch)

D1 D2 D3 F1(Control)

Test Sections

OriginalJul-98Jul-99

The control section has a higher SN because it has 2-ft extra base fill due to poor subgrade conditions

Maine DOT Post-InstallationMaine DOT Post-Installation

VADOT-Route 58 Rehabilitation VADOT-Route 58 Rehabilitation ProjectProject

VADOT-Route 58 Rehabilitation Project -VADOT-Route 58 Rehabilitation Project -Tack coat applied and geocomposite placementTack coat applied and geocomposite placement

Traffic over the geocomposite panelTraffic over the geocomposite panel

Asphalt placement Asphalt placement over the geocompositeover the geocomposite

ConclusionsConclusionsConclusionsConclusions The geocomposite drainage layer appears to be an effective alternative for

pavement drainage. Calculations based on time-to drain approach indicate:

Adequate infiltration rates to handle significant storm events. < 10 min. To drain the geocomposite layer. < 2 hours hours to drain the road even when placed beneath moderately

permeable dense graded aggregate base. I.E. Excellent drainage based on AASHTO 1998 criteria.

Four case studies in progress with 1 monitored study showing: Excellent to good drainage following major storm events. Geocomposite drains in subgrade found most effective, especially during spring

thaw. Geocomposite drains facilitated construction and may have improved roadway

section stiffness.

COMMENTS ?COMMENTS ?COMMENTS ?COMMENTS ?

QUESTIONS ?QUESTIONS ?