11/30/1998 Design of Roadway Drainage Systems Using Geocomposite Drainage Layers by Barry R. Christopher, Ph.D., P.E.

CONTENTS OF PRESENTATION
Water in Pavement Systems Design for Drainage Conventional Drainage Solutions Geocomposite Drainage Layer Solutions Drainage Requirements for Permeable Layer Geocomposite Drainage Effectiveness Cost-Benefit Edge Drain and Outlet Requirements Geotextile Filter Design Specifications Case Histories

CONVENTIONAL FLEXIBLE PAVEMENTS
Seal Coat Tack Coat Surface Course Prime Coat Binder Course Base Course Subbase Compacted Subgrade Natural Subgrade

LIFE-CYCLE COST ANALYSIS
PAVEMENT DESIGN ENVIRONMENT TRAFFIC MATERIALS FAILURE CRITERIA STRUCTURAL MODEL MINIMUM THICKNESS, etc. STRUCTURAL DESIGN LIFE-CYCLE COST ANALYSIS CONSTRUCTION COSTS RIDEABILITY

OPTIMUM INVESTMENT LEVEL
11/30/1998 OPTIMUM INVESTMENT LEVEL TOTAL COST PRESENT WORTH FUTURE INVESTMENT Maint., Rehab., User, etc. OPTIMUM INITIAL COST 50 % RELIABILITY (pavement condition) 100 %

CONSIDERATIONS IN PAVEMENT DESIGN
Continuous & Rapid Deterioration with Time Repeated & Dynamic Loading Different Load Magnitudes & Configurations Traffic Distribution and Growth Change Materials Properties & Characteristics Drainage Contamination of Road Materials

FAILURE CRITERIA IN PAVEMENTS
11/30/1998 FAILURE CRITERIA IN PAVEMENTS RUTTING FATIGUE CRACKING THERMAL CRACKING REFLECTION CRACKING CONTAMINATION DRAINAGE/ MOISTURE

MECHANISTIC-EMPIRICAL FRAMEWORK IN THE 2002 PAVEMENT DESIGN GUIDE.

ENVIRONMENTAL / CLIMATIC
FACTORS Temperature Precipitation Humidity Depth to Water Table Frost Susceptibility Capillary rise Potential

in the Pavement Structure Primary Cause of Distress
11/30/1998 Water in the Pavement Structure Primary Cause of Distress

11/30/1998

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

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 %

Effect of Moisture on Resilient Modulus
11/30/1998 Effect of Moisture on Resilient Modulus Resilient Modulus MR, ksi 16 14 12 10 8 6 4 2 100% AASHTO - T99 95% AASHTO - T99 10 20 30 40 50 60 70 80 90 100 % Saturation, S

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.

DRAINAGE Tire Subgrade

LOADED FLEXIBLE PAVEMENT
Direction of Travel Free Water Wedge Deflection of Aggregate Base Deflection of Subgrade Hydrostatic Pressure

CONTAMINATION / PUMPING
11/30/1998 CONTAMINATION / PUMPING HMA Base Subgrade

AGGREGATE PENETRATION
11/30/1998 AGGREGATE PENETRATION HMA Base Subgrade

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

Water is Violently Displaced Carrying Suspended Fines
Loaded PCC Pavement Free Water Hydrostatic Pressure or Water Jet Direction of Traffic Direction of Traffic Water is Violently Displaced Carrying Suspended Fines

11/30/1998 JOINT DETERIORATION

Water in Pavements Summary
11/30/1998 Water in Pavements Summary Stripping in HMA Loss of Subgrade Support Reduction of Granular Layer Stiffness Erosion of Cement-Treated Base Layers Reduction in the Pavement Service Life If Base Is Saturated for Sometime Debond between Layers

HOW TO ADDRESS THE PROBLEM?
11/30/1998 HOW TO ADDRESS THE PROBLEM? Pavement geometry (slopes and ditches) Crack sealing Treated Layer Thicker Layers Full Width Subsurface Drainage 0.02 m/m 0.04 m/m HMA 1 : 6 Treated base 1 : 4 Aggregate base Subgrade

11/30/1998

Through Permeable Surface
11/30/1998 Capillary Rise Through Permeable Surface Seepage Capillary Vapor Water Table Water Table

PAVEMENT OVERLAY SUMMARY
11/30/1998 PAVEMENT OVERLAY SUMMARY Excessive Moisture in Pavement Structures Has Been Identified as a Major Source of Failure in Pavements. There is a need for subsurface drainage Reflection of Cracks May Occur after One to Two Years of the Overlay Placement. Failures due to Drainage and Reflective Cracking Rarely Considered in Pavement Design & Rehabilitation Strategies. Is It Possible to Address Both Issues Simultaneously?

Three important components for a good pavement design
11/30/1998 Three important components for a good pavement design Drainage Drainage Drainage

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

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 log10W18 = (ZR)(S0) + (9.36)(log10(SN+1) log10[PSI/( )]/[ (1.094/(SN+1)5.19)] + (2.32)(log10MR)

AASHTO Guide for Design of Pavement Structures, 1993

Recommended Drainage Coefficient, mi, for Flexible Pavements
0.40 Very Poor 0.60 Poor 0.80 Fair 1.00 Good 1.20 Excellent Greater Than 25% 5-15% 1-5% Less Than 1% Percent of Time Pavement Structure is Exposed to Moisture Levels Approaching Saturation Quality of Drainage AASHTO Guide for Design of Pavement Structures, 1993

Rainfall Intensity for a 2-year, 1-hour Storm Event (FHWA, 1992)
11/30/1998 Rainfall Intensity for a 2-year, 1-hour Storm Event (FHWA, 1992)

US Map with AASHTO Climatic Zones
11/30/1998 US Map with AASHTO Climatic Zones B C E F D B A

WHEN IS THE OPTIMUM TIME TO MAINTAIN PAVEMENT
WHEN IS THE OPTIMUM TIME TO MAINTAIN PAVEMENT? HOW ABOUT A BETTER DESIGN! CONDITION EXCLENT VERY GOOD GOOD FAIR POOR 75% of service life $1 not spend here... Will cost $4-10 here 40% quality loss AGE (years)

11/30/1998 Pavement Drainage Christopher and McGuffey, 1997, NCHRP Synthesis 239, “Pavement subsurface drainage systems”

Use of Permeable Base in U.S.
11/30/1998 Use of Permeable Base in U.S.

Example of Separator Layer Envelope
11/30/1998 Example of Separator Layer Envelope 20 40 60 80 100 Aggregate Separator Layer Envelope Permeable Base Percent Passing Subgrade 0.01 0.05 0.1 0.5 1 5 10 50 100 Grain Size - mm

Geotextile Separator Layer Design
11/30/1998 Geotextile Separator Layer Design Check for Separation criteria (soil retention) Survivability and endurance criteria Clogging potential criteria* Permeability criteria*

Permeable Base Systems
11/30/1998 Permeable Base Systems Pavement Shoulder 10-year flow Permeable base Base layer Longitudinal pipe edge drain Rigid outlet pipe Ditch Shoulder Permeable base Base layer Pavement Subgrade Ditch Fabric Embankment

Design Considerations
11/30/1998 Selection of edge drain type Drainage capacity estimation Selection of materials for edge drain components Edge drain location Outlet design

Edgedrain/Outlet Joint
11/30/1998 Edgedrain/Outlet Joint Dual outlet systems are recommended Smooth, long-radius bends are preferred over sharp T-shaped bends

Headwall and Rodent Screens
Headwalls with removable rodent screens are recommended 11/30/1998 Headwall and Rodent Screens

Crushed Outlet Clogged Outlet
11/30/1998 Crushed Outlet Clogged Outlet

Results from FHWA Video Inspection Project
11/30/1998 Results from FHWA Video Inspection Project 35 % 35 % 13 % 17 % Edgedrains good Edgedrains non-functional Edgedrains not reviewable Outlets non-functional

11/30/1998 SUBSURFACE DRAINAGE OGDL EDGE DRAIN

Permeability Ability of materials to carry water
11/30/1998 Permeability Ability of materials to carry water Coefficient of permeability (k) Measure of permeability Rate of flow through a unit area with a unit hydraulic gradient Affected by Porosity Effective grain size, D10 Percent passing #200 sieve Measured in the lab: Falling head test Constant head test Field testing: Percolation test Field permeability testing device Tipping buckets

Influence of D10 on Permeability
11/30/1998 Influence of D10 on Permeability Gradation D (mm) k (m/day) 10 DGAB 0.10 1.2 Coarse Sand - 27 Pea Gravel 3.3 670 AASHTO No. 67 5.78 1585 AASHTO No. 57 6.01 2072 K (cm/sec)  D10 (mm)2

Movement Of Water Gravity, capillary action, vapor pressures
Granular materials  gravity v = ki (Darcy’s law) v = discharge velocity (not actual seepage velocity) k = coefficient of permeability i = hydraulic gradient Q = vA (Discharge = volume of flow per unit time): A = cross-sectional area normal to the direction of flow

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

Geocomposite Drainage Layers
11/30/1998 Geocomposite Drainage Layers Maine DOT

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

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

Geocomposite Drainage Layer Solutions - Replace OGAB
For Rigid Pavements Improved Design > Cd For Flexible Pavements Improved design life

Geocomposite Drainage Layer Solutions - Improve Performance of DGAB
Improved Pavement Design > m or Cd > SN Separation Improved long term performance Stabilization Improved construction Reinforcement Improved Support - LCR

Solutions to Reduce Capillary Rise
11/30/1998 Solutions to Reduce Capillary Rise Capillary rise can be reduced by introducing a barrier (capillary break) to reduce water migration to the pavement section. Capillary break Vapor Capillary Water Table Water Table

Geocomposite Layers for Drainage, Separation, and Reinforcement
11/30/1998 Geocomposite Layers for Drainage, Separation, and Reinforcement Drainage geonets can quickly remove subsurface water from the pavement Replace drainable aggregate layers Enhance the drainage of dense graded aggregate layers Provide a positive capillary break to: Reduce capillary rise issues Reduce damage caused by frost heave & subsequent thaw Effectively separate structural fills from the subgrade Reinforce the base course and restrain weak subgrade Strain energy absorber

Geocomposite Drain Requirements
Sufficient stiffness to support traffic without significant deformation under dynamic loading Inflow capacity > infiltration from adjacent layers Sufficient transmissivity to rapidly drain the pavement section and prevent saturation of the base Sufficient air voids within geo-composite to provide a capillary break

Drainage Geocomposite - Important Properties
Transmissivity = 4500 ft2/day (0.005 m2/sec) Estimated Discharge: 30 ft3/day /ft Creep Resistance under high Loads Long-term Resistance to Compression Stability Traffic Loads = Univ. of Illinois Study Effective Porosity = 0.7 Geotextile Filtration Requirements

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

RoaDrainTM Drainage System
11/30/1998 RoaDrainTM Drainage System Replaces OGDL Provides Excellent Drainage Capability Capillary Breaker May Provide Strain Energy Absorption Capabilities

RoaDrainTM Important Properties (Cont.)
Transmissivity = 4500 ft2/day (0.005 m2/sec): Transmissivity of 4in-OGDL (k =1000–3000 ft/day) = ft3/day/ft OGDL flow = 6–20 ft3/day/ft Transmissivity of RoaDrainTM = 1500 (considering an equivalency factor between RoaDrainTM and soil drains) RoaDrainTM flow = 30 ft3/day/ft

11/30/1998 Design of Flexible Pavements Incorporating Geocomposite Drainage Layers

Design Manual for Roadway Geocomposite Underdrain Systems: SCOPE
Design guidance for a new alternative drainage method Horizontal geocomposite drainage layer tied directly and continuously into an edge drain system. Tendrain™ by the Tenax Corporation) Current AASHTO and Corps of Engineers pavement design codes Application Used directly to replace drainable aggregate layers in rigid or flexible pavement systems, or Enhance the drainage of dense graded aggregate layers often used in flexible and rigid pavement systems.

Drainage Requirements for Permeable Layer
FHWA Demonstration Project 87: Drainable Pavement Systems, Participant Notebook Two approaches to the hydraulic design of a permeable layer: Time-to-drain Steady-state flow Two design approaches for determining the time to drain: AASHTO Percent Drained - 50 percent 85-Percent Saturation

Time-to-Drain Design Assumptions
11/30/1998 Time-to-Drain Design Assumptions During a rainfall event water infiltrates into the permeable base until it is saturated Excess rainwater runs off to a side ditch Time required to drain certain amount of water from the drainage layer after a rain event

Time-to-Drain qi Q qd Pavement Shoulder Permeable base Base layer
11/30/1998 Time-to-Drain qi qd Pavement Shoulder Q Permeable base Base layer

AASHTO Drainage Definitions (For Pavements - 50% time to drain)
11/30/1998 AASHTO Drainage Definitions (For Pavements - 50% time to drain) Quality of Drainage Excellent Good Fair Poor Very Poor Water Removed Within 2 Hours 1 Day 1 Week 1 Month Water will not Drain For Interstate highways: 50% drained in 2 hrs If heavy traffic, in 1 hr AASHTO Guide for Design of Pavement Structures, 1993

Design Standards For pavement rehabilitation, 85% saturation Excellent
11/30/1998 Design Standards For pavement rehabilitation, 85% saturation Excellent < 2 hours Good 2 to 5 hours Fair 5 to 10 hours Poor > 10 hours Very Poor >>> 10 hours

Recommended Drainage Coefficient, mi, for Flexible Pavements
11/30/1998 AASHTO Guide for Design of Pavement Structures, 1993

Factors Affecting The Design
11/30/1998 Factors Affecting The Design Pavement slopes Aggregate gradation Porosity and effective porosity Layer saturation Permeability

( ) Pavement Slopes S = + LR W S SX = + æ è ç ö ø ÷ 1 Tan A S SX ( ) =
11/30/1998 Pavement Slopes LR S SX SR A W ( ) S R x = + 2 5 . LR W S SX = + æ è ç ö ø ÷ 1 2 0.5 Sx SR S W LR Tan A S SX ( ) = æ è ç

Pavement Slopes Surface and subsurface slopes Always positive SR
11/30/1998 Pavement Slopes Surface and subsurface slopes Always positive SR Recommended slopes: 0.02 m/m (normal conditions) 0.025 m/m (high rainfall)

Time-to-Drain Calculation
11/30/1998 Time-to-Drain Calculation t = T x m x 24 m-factor (days) Time factor Time to drain (hrs)

Sl = LRSr/H Time to drain t = T x m x 24
where, t = time to drain in hours T = Time Factor m = “m” factor Sl = LRSr/H

How to Estimate Time to Drain (t)
11/30/1998 How to Estimate Time to Drain (t) Input: S and Sx W, H, k, gd, Gsb, WL (for permeable base) Interim Output: SR, LR, S1 {S1 = (LR x SR)/H} T for a desirable degree of drainage (U) N and Ne N = [1- {gd / (9.81 x Gsb)}] Ne = N x WL “m” factor: m = (Ne x LR2) / (k x H) Output: t = T x m x 24 Transmissivity

Time-to-Drain and Permeability Relationship
11/30/1998 Time-to-Drain and Permeability Relationship k = 153 m/day H = 0.15 m Ne = 0.25 LR = 7.6 m SR = 0.02 m/m 20 40 Percent Drained 60 k = 305 m/day 80 k = 915 m/day k = 610 m/day 100 1 3 5 7 Time to Drain, hrs

Time-to-Drain Sensitivity
11/30/1998 Time-to-Drain Sensitivity Factors affecting time-to-drain: Effective porosity Coefficient of permeability Resultant slope Resultant length Permeable base thickness

Coefficient of Permeability, m/day
Effect of k 11/30/1998 6 LR = 7.6 m H = 0.15 m U = 50% SR = 0.02 m/m 4 Time to Drain, hrs 2 305 610 915 1220 Coefficient of Permeability, m/day

Effect of SR 1 .8 .6 Time to Drain, hrs .4 .2 .02 .04 .06
11/30/1998 Effect of SR 1 LR = 7.6 m H = 0.15 m U = 50% Ne = 0.25 k = 915 m/day .8 .6 Time to Drain, hrs .4 .2 .02 .04 .06 Resultant Slope, m/m

Effect of LR 2 1 Time to Drain, hrs 3.6 7.2 10.8 14.4
11/30/1998 Effect of LR 2 SR = 0.02 m/m H = 0.15 m U = 50% Ne = 0.25 k = 915 m/day 1 Time to Drain, hrs 3.6 7.2 10.8 14.4 Resultant Length, m

Permeable Base Thickness, mm
11/30/1998 Effect of Thickness 1.5 SR = 0.02 m/m U = 50% Ne = 0.25 m/m k = 915 m/day LR = 7.6 m 1 Time to Drain, hrs .5 100 200 300 Permeable Base Thickness, mm

T for U = 50% Drained 7 5 3 Slope Factor (S1) 2 1 .01 .03 .10 .30 .60
11/30/1998 T for U = 50% Drained 7 5 3 Slope Factor (S1) 2 1 .01 .03 .10 .30 .60 Time Factor (T50)

RoaDrainTM Time to Drain
Case B - Beneath Pavement Time to Drain < 10 min Case A - Beneath Subbase for 15 in subbase with k = 1 ft/day Time to drain ~ 3 hours

Potential Cost Benefit

Layer Coefficient Ratio (LCR)
11/30/1998 Layer Coefficient Ratio (LCR) “Geogrid reinforcement of flexible pavements: a practical perspective” Zhao & Foxworthy, Geotechnical Fabrics Reports, (pp , May, 1999)

Edge drain Construction
11/30/1998 Edge drain Construction

Edge drain Flow Capacity
11/30/1998 Edge drain Flow Capacity Manning's equation for circular pipes: Q = x 10-3 D8/3 S1/2 n where: Q = pipe capacity, m3/day D = pipe diameter, mm S = longitudinal slope, m/m n = Manning’s coefficient

Flow Capacity of Circular Smooth Pipe
11/30/1998 Flow Capacity of Circular Smooth Pipe 0.100 Smooth Circular Pipe n = 0.012 75 mm 100 mm Slope, m/m 0.010 150 mm 0.001 10 100 1000 10,000 Pipe Capacity, m3/day

Flow Capacity of Circular Corrugated Pipe
11/30/1998 Flow Capacity of Circular Corrugated Pipe 0.100 Corrugated Circular Pipe n = 0.024 Slope, m/m 0.010 75 mm 100 mm 150 mm 0.001 10 100 1000 10,000 Pipe Capacity, m3/day

Outlet Spacing Hydraulic requirement: L < Q < 75m qd where:
11/30/1998 Outlet Spacing Hydraulic requirement: L < Q < 75m qd where: L = outlet spacing, m Q = pipe capacity, m3/day qd = design pavement discharge, m3/day/m

Outlet Spacing Maximum spacing = 250 ft Minimum diameter = 4 in.
11/30/1998 Outlet Spacing Maximum spacing = 250 ft Minimum diameter = 4 in. Estimated Discharge from Geocomposite Drain: 30 ft3/day /ft of road X 250 ft = 7500 ft3/day Pipe capacity, cu ft/day (Q) For 4” pipe at 1% grade, Q = cu ft/day

Rainfall Intensity for a 2-year, 1-hour Storm Event (FHWA, 1992)
11/30/1998 Rainfall Intensity for a 2-year, 1-hour Storm Event (FHWA, 1992)

Geotextile Filter Design
11/30/1998 Geotextile Filter Design Basic Principles Largest pores in geotextile < larger particles of soil Majority of pores > than smaller particles of soil High porosity, high flow rate See FHWA Geosynthetic Design Manual (Holtz, Christopher and Berg, 1998)

Geotextile Filter Design
11/30/1998 Geotextile Filter Design Step 1.Determine the gradation of the material to be filtered. Above and below the geocomposite drainage layer D85, D15 and percent finer than a No. 200 sieve. Step 2. Determine the permeability of the base/subbase kgeotextile directly above the geocomposite drainage layer. Step 3. Apply design criteria for AOS and k requirements AOS < D85 base/subbase (For upper geotextile) AOS < 1.8 D85 subgrade (For the lower geotextile)* kgeotextile > kbase/subbase Ψ > 0.1 sec-1 Step 4. Survivability requirements: AASHTO M288 (1997)

Survivability Requirements
11/30/1998 Survivability Requirements

GEOCOMPOSITE SUBSURFACE DRAINAGE LAYER
11/30/1998 Specifications GEOCOMPOSITE SUBSURFACE DRAINAGE LAYER

11/30/1998 Construction

Some Case Studies

Maine DOT - Frankfort to Winterport Highway

11/30/1998

11/30/1998 Different Geosynthetic Pavement Support Applications, Different test sections

Drainage Test Sections
11/30/1998

Geocomposite Pavement Drains
11/30/1998 Geocomposite Pavement Drains

11/30/1998

11/30/1998 Underneath HMA

11/30/1998

Important Parameters Flow through pavement and base
11/30/1998 Important Parameters Flow through pavement and base at outlets (time to drain) Pore pressure base, sub base & subgrade positive & negative Moisture content Long-term support pavement, base and sub base Road surface movement Water level Temperature with depth Weather rainfall & temperature atmospheric pressure

Tip Buckets Installed in Each Test Section
11/30/1998 Tip Buckets Installed in Each Test Section Your Text Here

Tilt Bucket Schematic 11/30/1998

Monthly Discharge Volumes (Per Length of Drain and Rainfall)

11/30/1998

FWD Testing D1 D2 D5 D4 D3 D6 D7

Falling Weight Deflectometer (FWD) Results Maine DOT
11/30/1998

Falling Weight Deflectometer (FWD) Results (Drainage Sections), Maine DOT
11/30/1998

Maine DOT Post-Installation
11/30/1998

Summary of Performance
11/30/1998 Maine DOT - Summary of Performance Discharge during the first year of monitoring corresponds strongly to precipitation events and water table levels. The quality of drainage is good to excellent. Structural support = to section with 18 inches of additional stabilization aggregate. Tri-planar was an effective capillary barrier and eliminated frost heave; No physical changes were observed.

Wisconsin DOT, Highway 60

VADOT-Route 58 Rehabilitation Project

Route 58 Rehabilitation Project
2-lane in each direction 24ft wide (3ft inner and 4ft outer shoulders) 2% surface slope (CL center line) 9in reinforced jointed concrete 61.5ft) 6in cement treated subgrade 9in HMA overlay (3 layers): 1in SM, 2in IM, and 5.5in BM Geocomposite installed in the passing lane The project has edge drain

Tack coat applied and geocomposite placement

Traffic over the geocomposite panel

Asphalt placement over the geocomposite

HMA Overlay

HMA over Geocomposite

FWD Testing

FWD Testing Testing on outside wheel path of both lanes
75’ intervals Four load levels: 6kips, 9kip, 12kip, and 16kip Testing started at 500ft before Geocomposite (MP 10.3; Geocomposite at MP 10.39) 9in JRCP 9in HMA 6in Cement-Treated Subgrade 6in HMA 3in HMA + Geocomposite 9in JRCP 6in Cement-Treated Subgrade

Center Deflection (Do)
6kip 9kip 12kip

Backcalculated Moduli Treated Subgrade Modulus
HMA Modulus Subgrade Modulus Treated Subgrade Modulus

Backcalculated Moduli
9in HMA 738ksi; Stdv=136ksi 6in HMA 738ksi 3in HMA + Geocomposite 270ksi, Stdv=41ksi 9in JRCP 1349ksi; Stdv=437ksi 9in JRCP 1349ksi 6in Cement-Treated 25.2ksi; Stdv=4ksi 6in Cement-Treated (25.2ksi) Subgrade 14.0ksi; Stdv=2.4ksi Subgrade (14.0ksi)

Rutting Test Results Rutting test was run on HMA backed by Geocomposite No rutting after 16, oF Pressure = 120psi

GPR Survey

I-64 Case Study AASHTO Overlay Design
11/30/1998 I-64 Case Study AASHTO Overlay Design Determination of Overlay Thickness: Dol = A (Df – Deff) Df = overall slab thickness (9in); Deff = effective thickness (considering pavement distresses, 8in) Dol = 4in

I-64 Case Study Mechanistic Approach  Finite Element Analysis
11/30/1998 Mechanistic Approach  Finite Element Analysis 4in Base 25,000psi N/A Geocomposite 9in JRC Subgrade 12,000psi 4.5in HMA Design 1 4.5in SMA Design 2

I-64 Overlay Study Project Description
11/30/1998 I-64 Overlay Study Project Description Traffic Analysis (10-year Design): 10.9 millions ESALs JRCP (Mean Joint Load Transfer = 61.6%) Mean Static k-value = 118 pci Slab Thickness = 9in  Effective Slab Thickness = 8.0in

11/30/1998 I-64 Case Study

Shear Strain in Concrete
w/ Geocomposite w/o Geocomposite

Crack Initiation: Mode II
Shear Stress with Geocomposite Shear Stress without Geocomposite

Mechanistic Approach  Finite Element Analysis
11/30/1998 I-64 Case Study Mechanistic Approach  Finite Element Analysis Rutting (in) Fatigue (yr) Reflective (yr) Criteria 9.6 15 0.23 >10 Design 1 5.2 Design 2 Final Design: Geocomposite + 4.5in HMA

Maine DOT – Madawaska US Route 1 Project

Excavation of 1-ft subgrade
Note: without this geocomposite, additional 1-ft cut is required

Deploying Geocomposite Panel
Average installation time ~ 4 min. for 13’x 200’ panel.

Base course aggregate (3. 5 in
Base course aggregate (3.5 in. max) placed and compacted over the geocomposite

Ft. Williams Pkw, Alexandria, VA
11/30/1998

11/30/1998 Ft. Williams Pkw, Alexandria, VA

11/30/1998

11/30/1998 Conclusions The Tendrain geocomposite drainage layer is 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. Five case studies in progress with 3 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. FEM study shows good potential for Strain Energy Absorption

11/30/1998 QUESTIONS ?

11/30/1998 Design of Roadway Drainage Systems Using Geocomposite Drainage Layers by Barry R. Christopher, Ph.D., P.E.

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11/30/1998 Design of Roadway Drainage Systems Using Geocomposite Drainage Layers by Barry R. Christopher, Ph.D., P.E.

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