Geosynthetics have revolutionized road construction, yet their full potential remains underutilized due to insufficient knowledge among industry experts. Understanding the functions, application terms, and calculation methods for these game-changing materials is essential for maximizing their benefits .
The Promise of Geosynthetics in Road Construction
Despite successful experience with geosynthetic usage and expanding product ranges, many road industry experts are either insufficiently knowledgeable about, or totally unaware of, geosynthetic benefits. This knowledge gap causes experts to lose sound opportunities to solve simply and efficiently many road construction problems, such as :
Swamp and weak soil foundations
Surface deformation and rutting
Frost heaving
Reflective surface cracks
Geosynthetics are a certainly promising trend of road construction, and their functions, application terms, and calculation methods should be scrutinized to utilize their potential to the highest possible extent .
Types of Geosynthetic Materials for Road Pavements
Depending on the geomaterial purpose, the benefit derived can lie in initial (construction) cost reduction and/or repair cost reduction over the service life .
The following geosynthetic materials are used as interlayers in road pavements :
Woven geotextile fabrics
Nonwoven geotextile fabrics
Flat biaxial geogrids
Geomats
Volumetric geogrids (geocells)
Composite geomaterials
Selection Criteria: Technical and Economic Evaluation
The selection of geosynthetic material is done by comparison of technical and economic features of road pavement versions with and without geosynthetic materials. The technical effect as compared to conventional solutions should be paid due attention .
The use of geosynthetics boosts the reliability of road structures as well as construction quality, which sometimes cannot be numerically evaluated. For technical feasibility purposes, this benefit—on account of a road structure's fitness to work and operational properties—can be evaluated higher than the initial expenditure saving of the alternative variants under comparison .
Primary Functions in Road Pavements
Geosynthetics are used in road pavements as :
Reinforcement and separation layer: For reinforcement of aggregate of loose, granular materials (macadam, gravel, macadam-gravel-sand mixtures, slag, etc.) or temporary pavement
Separation layer: At the border of large-grained materials and soil
Protection-drainage layers: Where the draining sand layer contacts the embankment soil
Protection layers: Under precast concrete slabs
Reinforcement (crack preventing) layer: For reinforcement of asphalt pavements
The Benefit of Geosynthetic Application
The benefit of geosynthetics application is especially tangible in :
Construction, renovation, and repair of motorways of a high standard
Extreme Northern weather conditions (handling earth at temperatures below zero)
Unfavorable soil and hydrology conditions (weak foundations, swamp soil, special soils)
Calculation Methods per Road Industry Norms
Geosynthetics' effect on a road pavement structure as per Road Industry Norms (RIN) 218.046-2001 is measured by three methods (CREDO RADON 3.4 program) :
1. RIM 218.5.002-2008: Recommendations for usage of polymer geomats (geogrids) in reinforcement of road pavement layers of granular materials
This method addresses the reinforcement of road pavements and layer separation of road pavement aggregates of untreated granular materials and underlying soil layers through geosynthetic materials—flat geogrids, geomats, woven geosynthetic fabrics, and geocomposites. As a result, road pavement reliability and durability grow, while the thickness of road pavement layers of conventional materials, particularly granular-material aggregates, is reduced .
2. RIM 218.5.003-2010: Recommendations for geosynthetic material usage in motorway construction and repair
3. RIM 218.5.001-2009: Recommendations for usage of geomats and flat geogrids in reinforcement of asphalt and concrete layers of advanced pavements during motorway overhaul and repair
Optimal Conditions for Reinforcing Geosynthetics
The most rational way of using reinforcing geosynthetics is achieved under the following conditions :
When an aggregate of large-grained material is placed right on the subgrade (no sub-base layer), or a sub-base layer of uniform sand is placed instead of a protective aggregate layer of 10-to-20-cm thickness required in this case
For heavy-duty roads
For construction under unfavorable conditions (swamp subgrade, aggregate use for construction vehicles traffic, long period between aggregate placement and covering by overlying layers, phased construction and renovation, heavy-traffic road repair)
For multilane highways with most of the truck traffic along the outer lanes equipped with underneath interlayers
In cases when the safety factor values per RIN 218.046-01 in terms of sub-base sand layer shear are the lowest for flexible pavements as compared to the other criteria
Calculation Methodology
Reinforced road pavements are calculated per RIN 218.046-01, with amplifier ratio depending on :
Geomaterial deformation properties
Layer thicknesses
Road pavement and subgrade mechanical properties
The reinforcing geomaterial has the highest influence on the value of active shear stresses on the subgrade layer located right under the reinforced layer .
Practical Implications
For pavement engineers, understanding these calculation methods enables :
More accurate prediction of pavement performance
Optimization of layer thicknesses
Justification of geosynthetic selection decisions
Quantification of lifecycle benefits
Conclusion
Geosynthetics offer proven benefits for road pavement construction, yet their full potential requires proper understanding of selection criteria, application methods, and calculation approaches. By scrutinizing these factors, engineers can utilize these game-changing materials to the highest possible extent, solving complex road construction problems simply and efficiently .
At HZ Geotextile, we offer a comprehensive range of geosynthetics for road applications, backed by technical support and application engineering. Contact our team for assistance with material selection and design calculations for your next pavement project.
