The choice between woven and nonwoven geotextiles—or between geotextiles and geogrids—is a fundamental decision in roadway design. Each material type offers distinct advantages, and the optimal selection depends on subgrade conditions, aggregate quality, and project type .
The Foundational Framework
A classic comparison published in Geotechnical Fabrics Report provides lasting guidance for geosynthetic selection in roadway applications . The framework distinguishes between two roadway types and multiple subgrade conditions, offering specific recommendations for each scenario.
Temporary Gravel-Surfaced Haul Roads
Temporary roads face different demands than permanent structures. They must support construction traffic for a limited period, after which they may be removed or incorporated into permanent works.
For Clayey or Silty Subgrades :
Required: A nonwoven separator geotextile must be used in conjunction with a clean base aggregate
Why: Nonwoven geotextiles provide excellent filtration and separation, preventing fines migration from the clay subgrade into the aggregate. Clean aggregate ensures good drainage and strength
If choked aggregate is used: If a choked aggregate like general crusher run is specified, then either a geotextile or a biaxial geogrid that has good aperture stability and appropriate size is recommended
Recommended: A biaxial grid with good aperture stability and appropriate size, or a woven geotextile that has reasonable interface friction with the sand and the aggregate
Why: Sandy subgrades derive stability from confinement and friction. Geogrids interlock with sand grains, while woven geotextiles provide high interface friction. Both mechanisms improve load distribution
Permanent Roadway Structures
Permanent roads require longer design lives and must withstand repeated traffic loading over decades. Subgrade conditions determine the appropriate geosynthetic approach .
For Clayey or Silty Subgrades with CBR < 3 (Very Soft) :
Approach: A working platform can be built using the temporary road methods upon which the conventional road can be constructed
Why: Very soft subgrades cannot support construction equipment or pavement loads directly. A stabilized working platform provides a firm foundation for subsequent layers
For Clayey or Silty Subgrades with CBR 3-8 (Soft to Medium) :
Recommended: A separator geotextile to protect the base aggregate should be included if there is any potential for degradation due to water intrusion or frost heave
Why: Even moderately strong subgrades can generate fines migration under repeated loading, especially when water is present. The geotextile prevents contamination of the aggregate base, preserving its structural properties
Recommended: A biaxial geogrid that has good aperture stability and appropriate size to reinforce the base aggregate
Why: Geogrid reinforcement is particularly helpful when poor-quality stone must be used and when the aggregate thickness is small. The geogrid interlocks with aggregate, distributing loads and reducing required thickness
Material Property Implications
Nonwoven Geotextiles
Primary functions: Filtration, separation, drainage
Key properties: High permittivity, good conformability, moderate strength
Best applications: Clay subgrades, wet conditions, drainage layers, protection
Woven Geotextiles
Primary functions: Reinforcement, separation, stabilization
Key properties: High tensile strength, low elongation, high interface friction
Best applications: Sand subgrades, load support, reinforcement
Geogrids
Primary functions: Reinforcement, confinement, stabilization
Key properties: Aperture stability, tensile strength, interlock capability
Best applications: Aggregate reinforcement, weak subgrades, thin aggregate sections
Decision Matrix
Additional Considerations
Water Sensitivity
The recommendation for separator geotextiles in CBR 3-8 clay subgrades includes a critical qualifier: "if there is any potential for degradation due to water intrusion or frost heave" . This highlights the importance of site-specific hydrology in geosynthetic selection.
Aggregate Quality
Geogrid reinforcement is "particularly helpful when poor quality stone must be used and when the aggregate thickness is small" . For projects with limited aggregate access or strict thickness constraints, geogrids can extend material performance.
Interface Friction
For woven geotextiles on sandy subgrades, "reasonable interface friction with the sand and the aggregate" is essential . This property should be verified through direct shear testing for critical applications.
Aperture Stability
For geogrids, "good aperture stability and appropriate size" are emphasized repeatedly . The grid openings must be sized to accommodate aggregate particles while maintaining dimensional stability under load.
Practical Application
When specifying geosynthetics for roadway projects, follow this process:
Characterize subgrade: Determine soil type and CBR through geotechnical investigation
Assess project type: Temporary or permanent? What are the performance requirements?
Evaluate site conditions: Water table, frost potential, aggregate availability
Select material type: Use the decision matrix above to identify appropriate geosynthetic category
Verify properties: Ensure selected product meets specification requirements for the intended function
Consider combinations: Some applications benefit from geotextile + geogrid combinations
Conclusion
The choice between woven and nonwoven geotextiles—and between geotextiles and geogrids—is not arbitrary. It should be guided by subgrade conditions, project type, and site-specific factors. The framework established in this classic comparison continues to inform sound engineering decisions .
At HZ Geotextile, we offer a full range of woven and nonwoven geotextiles, as well as geogrids, for roadway applications. Contact our engineering team for assistance with material selection based on your specific subgrade conditions and project requirements.
