1. Geocomposite Subsurface Drainage Systems
11/30/1998
Geocomposite Subsurface Drainage Systems
Presented by:
Developed by: Aigen Zhao, PhD, PE
Tenax Corporation
VP/Engineering

2. CONTENTS OF PRESENTATION
Water in Pavement Systems
Conventional Drainage Solutions
Geocomposite Drainage Layer Solutions
Drainage Requirements for Permeable Layer
Geocomposite Drainage Effectiveness
Cost Benefits
Case Histories

3. 11/30/1998

4. Related References
FHWA, 1992, Demonstration project 87: “Drainable pavement systems”, Participant Notebook, FHWA-SA
US Army Corps of Engineers, 1992, “Engineering and design drainage layers for pavements”, Engineer Technical Letter, , 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.

5. 11/30/1998
Standing water in a pavement indicates low permeability and poor drainage

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

7. Water 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

8. Severity factor measures the relative
damage between wet and dry periods
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.

9. AASHTO Drainage Definitions
11/30/1998
AASHTO Drainage Definitions
Quality of Drainage
Excellent
Good
Fair
Poor
Very Poor
Water Removed Within*
2 Hours
1 Day
1 Week
1 Month
Water will not Drain
*Based on time to drain
AASHTO Guide for Design of Pavement Structures, 1993

10. Design for Drainage (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

11. Recommended Drainage Coefficient, cd, for Rigid Pavements
11/30/1998
Recommended Drainage Coefficient, cd, for Rigid Pavements
AASHTO Guide for Design of Pavement Structures, 1993

12. By, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.
Recommended values for drainage modifier, mi, for untreated base and subbase materials in flexible pavements (AASHTO, 1993).
Quality of
Drainage
Percent of time pavement is exposed to moisture levels approaching
saturation
Less than 1%
1 to 5%
5 to 25%
More than 25%
Excellent
1.20
Good
1.00
Fair
0.80
Poor
0.60
Very Poor
0.40
Page. 6 Table 2 - from the Design Manual for Roadway Geocomposite Underdrain Systems
By, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.

13. Components of a Drainable Pavement
11/30/1998
Components of a Drainable Pavement
Christopher and McGuffey, 1997, NCHRP Synthesis 239, “Pavement subsurface drainage systems”

14. Time to Drain For two lane road - Lane width = 24 ft, Slope = 0.01
Base k time to drain Quality
OGB ft/day 2 hrs to drain Excellent
DGAB ft/day 1 week Fair
DGAB w/ fines 0.1 ft/day 1 month Poor
Reality no drains does not drain Very Poor

15. TRADEOFF OF STABILITY AND DRAINABILITY OF OGBC
“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”

16. A Tri-planar Drainage Geocomposite Structure: RoaDrainTM
11/30/1998
A Tri-planar Drainage Geocomposite Structure: RoaDrainTM

17. New Alternative Drainage Material: Geocomposite Drainage Layers
11/30/1998
New Alternative Drainage Material: Geocomposite Drainage Layers
Maine DOT

18. Uses of Horizontal Geocomposite Drainage Layers
11/30/1998
Uses of Horizontal Geocomposite Drainage Layers

19. Separation between new asphalt overlay and subbase
Tri-Planar RoaDrain Geocomposite to Replace Drainable Aggregate in Flexible Pavement Systems
Asphalt Pavement
Excellent Drainage
Enhanced design life
Energy absorbing to mitigate reflective cracks from the existing PCC base
Separation between new asphalt overlay and subbase

20. Geocomposite to Replace Drainable Aggregate in Rigid or Flexible Pavement Systems
Drainage
For Rigid Pavements
Excellent drainage
Improved Design
> Cd

21. Enhance Drainage of Dense Graded Base by Shortening Drainage Distance
Improved Pavement Design
> m or Cd
> SN
Separation
Improved long term performance
Stabilization
Improved construction
Reinforcement
Improved Load Support

22. Geocomposite Drain Requirements
11/30/1998
Geocomposite 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.

23. RoaDrainTM – Important 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

24. Fatigue Test Setup and Representative Results (Univ. Of Il
Fatigue Test Setup and Representative Results (Univ. Of Il. Advanced Transportation Research and Engineering Lab)
11/30/1998

25. Potential Cost - Benefit

26. By, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.
Comparison of drainage performance with and without RoaDrain geocomposite drainage net.
RoaDrain only
Base drainage only
RoaDrain
under base
Resultant slope
0.02 1
Resultant length
24 feet 24
Thickness
Effective porosity
0.69
0.15
Transmissivity
4500
Results
Slope factor:
0.48 M:
0.088 86
Time to drain (hours):
840
0.86
Page. 21 Table 3 - from the Design Manual for Roadway Geocomposite Underdrain Systems
By, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.

27. Equivalency of RoaDrain to 4” OGBL – flow capacity
4”- OGBL with (k =1000 – 3000 ft/day) transmissivity = ft3/day/ft
Flow = 6 – 20 ft3/day/ft
RoaDrain Synthetic Drainable Base Layer (SDBL) transmissivity = 1500 and 2% after considering an equivalency factor between geocomposite drain and soil drain.
Flow = 30 ft3/day/ft
SDBL > OGBL

28. Frost Heave & RoaDrain as a Capillary Barrier
11/30/1998
Frost Heave & RoaDrain as a Capillary Barrier
Frost heave refers to the raising of a surface due to the formation of ice lenses in the underlying soil.

29. Solutions to Reduce Frost Damage
11/30/1998
Solutions to Reduce Frost Damage
U.S. Army Corps of Engineers (1963):
Limit the amount of frost-susceptible soil subjected to freezing temperatures.
Design of adequate bearing capacity during the most critical climatic period
a significant increase in aggregate thickness

30. Solutions to Reduce Frost Damage – RoaDrain Capillary Break
11/30/1998
Solutions to Reduce Frost Damage – RoaDrain Capillary Break
Pavement
Non-frost susceptible base
Frost penetration depth
No this kind of ice lens
Frost susceptible soil
RoaDrain Capillary Barrier
Water table
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

31. Freezing did not cause any observable physical changes
US Army Cold Regions Research and Engineering 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”

32. Maine DOT Field Study Frankfort–Winterport Route 1A

33. 11/30/1998

34. 11/30/1998

35. Drainage Test Sections
11/30/1998
Drainage Test Sections

36. Geocomposite Pavement Drains
11/30/1998
Geocomposite Pavement Drains

37. Construction Details Preparing Collection Pipe Ditch

38. Construction Details Collection Pipe Inlet/Outlet System

39. Construction Details Geocomposite Placement
Plastic ties being secured
Seams sewn
4 man-hours per 100’ of installation

40. Construction Details Geocomposite Placed Above Base Course cont.
Base course graded
Tack coat applied
Geocomposite placed
Pavement surface placed

41. Drainage Discharge

42. Drainage Discharge

43. RoaDrain – 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.

44. 11/30/1998
Falling Weight Deflectometer (FWD) Results (Drainage Sections), Maine DOT
The control section has a higher SN because it has 2-ft extra base fill
due to poor subgrade conditions

45. Maine DOT Post-Installation
11/30/1998
Maine DOT Post-Installation

46. VADOT-Route 58 Rehabilitation Project

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

49. Traffic over the geocomposite panel

50. Asphalt placement over the geocomposite

51. 11/30/1998
Conclusions
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.

52. 11/30/1998
QUESTIONS ?
COMMENTS ?