Mechanistic Modeling, Full-scale Load Testing for Development and Validation of Structural Design Methods, LCCA, Maintenance Criteria, and Guide Specifications for Permeable Pavements

Focus Area

Water Quality/Wetlands


Natural Resources




Over $750k


2-3 years

Research Idea Scope

The most commonly used fully permeable pavements are porous asphalt (PA) (excluding open-graded friction courses), pervious concrete (PC), and permeable interlocking concrete pavement (PICP). Unlike impervious pavements, permeable pavements must rely on structural design methods that account for long-term saturated soil subgrades from stormwater-filled void spaces within high porosity, open-graded aggregates. Traditionally, pavement design encourages drainage to reduce or eliminate structural weakness of saturated subgrades. The core barrier to adoption is providing reliable design methods that result in acceptance of higher loads than the current limitations prescribed for permeable pavements. The technical means exist to develop permeable pavement design methods that account for long-term (intentionally) saturated subgrades. Overcoming this barrier to adoption by civil engineers responsible for roads and/or stormwater management is creating practitioner-ready, easy-to-use, reliable design procedures that frame structural design life (typically in 80kN single axle loads or ESALs, or Caltrans Traffic Index). The deliverables needed are design tables or pavement section catalogs accompanied by design procedures. There will different structural design procedures for PA, PC and PICP since their structural response to loads varies. The sine qua non approach to creating these deliverables is through full-scale load testing that validates and/or calibrates existing mechanistic models of permeable pavements. Task 1: Conduct a literature review and field survey to identify critical responses, failure mechanisms, appropriate performance transfer functions, and modeling assumptions for mechanistic analyses of PA, PC and PICP under truck loading (80 kN axle loads). Task 2: Measure pavement deflections in the field on several PA, PC and PICP locations with known materials and subgrades to characterize effective stiffness of the different layers in the structures for use in modeling. This characterization may be done with a falling weight deflectometer and/or a Benkelman Beam with applied loads. Task 3: Perform mechanistic analyses of PA, PC and PICP to develop design tables following the approach documented in California Department of Transportation (Caltrans) Research Report CTSW-RT-10-249.04 Laboratory Testing and Modeling for Structural Performance Of Fully Permeable Pavements Under Heavy Traffic: Final Report for development of structural design tables and CTSW-RR-09-249.04 for PA, PC and PICP. The latter would be tested with stabilized permeable bases per the (latter) report’s recommendations. Task 4: Prepare a plan for validation with accelerated load testing based on the results of the mechanistic analysis. Task 5: Test structural responses and, if possible, failure of up to three test section each of PA, PC and PICP structures in dry and wet (saturated) conditions on a weak subgrade with accelerated load testing. While yet to be demonstrated, maximum loads may be three to five million ESALs. Monitor surface infiltration using ASTM C1701/C1781. Task 6: Analyze the results of the HVS testing and calibrate mechanistic models to create/revise/update PA, PC and PICP structural design methods where necessary. Task 7: Write a final report documenting the results of all tasks in the study with design tables and methods. Task 8: Conduct life cycle cost analyses that include maintenance considerations/criteria. LCCA analysis will also include offsite benefits and costs, as these impact costs. Task 9: Develop construction guidelines and specification recommendations that could be used by state DOTs. Task 10: Present findings to NCHRP and at Transportation Research Board and AASHTO meetings.

Urgency and Payoff

For state DOTs, there is increasing opportunity for permeable pavements to reduce stormwater runoff and local flooding, thereby increasing the resilience of the road infrastructure by providing water storage within or next to roads and parking lots. Permeable pavements represent another tool in pavement design, specifications and maintenance tool boxes for DOTs that is currently untapped. Moreover, permeable pavements can help DOTs meet National Pollution Discharge Elimination System (NPDES) and Transportation Separate Storm Sewer System (TS4) permits by reducing water pollution and related runoff volumes. Besides mitigating runoff and pollution, permeable pavements can also increase aquifer recharge, a pressing need in the semi-arid Southwestern U.S and have enhanced safety and comfort attributes compared to traditional pavements. Reduced water pollution to water bodies and loss of economic benefits from fishing and recreation Reduction or elimination of storm sewer pipes and drainage appurtenances Reduced land costs/use for stormwater retention/detention facilities Reduced waste treatment plant costs for processing combined stormwater and sanitary sewage Reduction in use of deicing materials and related water pollution Reduction in local flooding, related property damage and accident risks from flooded pavement Enhanced safety on roadways from improved visibility, improved braking and a reduction in hydroplaning potential Reduced pavement noise Protection of environmentally sensitive streams, lakes, wetlands and estuaries Increased nearby tree health and longevity

Suggested By

Becky Humphreys AFB65 6143871125

[email protected]