The applications of geosynthetics in construction of roadways and pavements offer advantages in stability, drainage, and long-life features. Selection, therefore, is a project-dependent task that will require thoughtful consideration of several factors. This blog explains the key considerations when making such decisions. The decision to choose a combination of products for pavement engineering boils down to seven areas that affect the end project itself. These include: Structural Design, Materials Science, Traffic and Loading, Drainage and Hydraulics, Environmental Factors, Construction and Maintenance, and finally, Design Standards and Methods defined by AASHTO, ASTM, NHAI or other governing bodies. With these components affecting the design, and outcomes comes the question of what is the right design to start with and then what materials are needed to achieve the end result.
One of the reasons geosynthetics score over traditional materials, which remain in wide use, are their longevity, and superior ability to improve the quality of the project and outcomes. With polymer based materials comes inherent longevity which means reduced maintenance cycles, and lesser hazards.
The use of these materials is because deploying them makes paved roads not just physically stronger, but chemically, functionally and environmentally superior, alongside cost advantages. Each of the below uses form key components of transportation infrastructure planning because of their ability to address soil stability, improve pavement performance, and reduce settlement, and improve the overall longevity of the road.
Geosynthetics are chosen for four broad areas of application in roadway and pavement construction. Geosynthetic products are materials placed in or under pavement structures to improve service performance by reinforcing the soil and improving the soil’s physical characteristics. Their uniqueness makes them valuable, and preferred in modern-day construction. Apart from the structural enhancements that it provides, there are also other considerations that make it a favored choice today.
This process is of particular value in soft soils conditions, or unstable soils. By using products such as geogrids, or geocells, site engineers can prevent settlement and deformation, enhance load bearing capacity and reduce soil erosion. Each product renders improvements in soil mechanical properties, and while on a case to case basis the specifics will change, we can broadly look at the following reasons to choose geosynthetic materials for roadway stabilization. A core feature is the stiffness of soil-geosynthetic composite in roadway performance through the lateral restraint applied on the confined material.
Refers to the process of restoring or improving the condition of an existing paved road, which has degraded. This can take on many forms, depending on the technique of rehabilitation, such as Full Depth Reclamation ((FDR), Cold In-Place Recycling (CIR) or Hot In-Place Recycling (HIR). However, this is dependent on the condition of the pavement, and needs to be examined in the context of environmental factors, and an analysis of the type of rehabilitation needed (whether the road needs retexturing, surface treatment, repair etc.) In choosing geosynthetics for this use case, we look at specific improvements that these materials bring.
Supports pavement layers and reduces deflection. This is typically an issue or challenge that needs resolving in roads where there’s high traffic, areas with soft soils, or if undertaking FDR techniques. Geogrids and geotextiles can often be used in such cases.
Helps distribute traffic loads and reduces cracking, which is important for Cold In-Place Recycling (CIR) and Hot In-Place Recycling (HIR) techniques. By using a geosynthetic product, in these contexts, we work to improve the load bearing capacity, and minimize reflective cracking. Geogrids, or geocomposites are often used to thin or weak pavements, or conditions with extreme temperatures. Geogrids offer a 100-1000 kN/m tensile stiffness to improve pavement conditions.
Geosynthetics (geotextiles, geogrids, geocomposites) are used to enhance interlayer friction, improving pavement stability and durability. This process enhances bonding between pavement layers without which paved roads undergo delamination, or separation of the layers, leading to unstable roads. Through CIR, HIR or overlay and repair techniques, new interfaces are developed, thus reducing interface shear failure.
In many geotechnical situations, water permeability within the subgrade, and base grade is an important consideration. Take for example, coastal highways, or roads within ports, mines or abutments under bridges. In such contexts, with heavy moisture saturation, drainage is an important part of the design stage itself. Here, geotextiles which allow for planar flow and minimize pore pressure, and thus minimizing settlement are often chosen for their ability to reinforce, separate and drain –altogether.
With pavement rehab, the need to improve fatigue resistance of the surface road, becomes a core goal. Roads such as truck routes, industrial parks, inter-state highways, or the kind which sees heavy vehicular traffic or those with high speed requirements are among common sites where fatigue resistance is affected over a period of time. Roads that also have cracking (longitudinal, transverse, or alligator) also become ideal use cases for rehabilitation using geosynthetics as they improve the tensile strength of the structure and a host of other features that make them optimal materials for this purpose.
Base course reinforcement refers to the technique used in pavement construction to improve the structural integrity and performance of the base layer, which lies directly beneath the surface course of a road or pavement structure. The objective of this reinforcement is to provide improved load bearing capacity, especially in soft soils, reduce rutting and deformation, improve stress distribution and to extend the service life of the pavement itself. When used in conjunction with geosynthetic materials, typically geogrids, the higher tensile strength and other factors mean reduced material costs, resistance to fatigue cracking, and better performance under heavier loads. By using geogrids, we can confer the following advantages through confinement of soil, and tensioned membrane effect.
A stable subgrade forms the basis of a strong foundation for a pavement structure (all of the pun intended). Without a stable subgrade, the entire pavement structure can be compromised easily, and there arises a likelihood of localized failures in the pavement. When stabilized well, and correctly, we can even design thinner pavements, and reduce the overall cost of construction. By using geogrids here, there is a lateral confinement of the soil, which allows for load spreading over a wider area. Since it’s also indifferent to moisture levels, it helps manage the effect of moisture on the subgrade performance.
For the longest time, road construction has meant using traditional methods of pavement design –which includes excavation of the subgrade, reinforcement through chemical or mechanical means, and applying reinforcement. The downside of this standard approach is that roads are susceptible to environmental forces such as torrential rain, and don’t withstand repetitive loading of traffic –especially under high vehicular traffic conditions.
Layer |
Geosynthetic Type |
Effects on Soil Properties |
|---|---|---|
|
Subgrade
|
Geogrid or Geotextiles
|
Lateral Restraint (increases bearing capacity), Tensioned membrane effect (vertical support under deformation), sepration (prevents mixing of layers), Does not significantly alter inherent soil properties
|
|
Base / Subbase
|
Usually Geogrids
|
Increased stiffness (mechanically stabilized layer), Improved load distribution (reduced stress on subgrade), Enhanced shear strength (due to increased mean stresses)
|
|
Asphalt
|
Various (less common)
|
Increased tensile strength (migrates reflective cracking), Improved fatigue resistance (extends pavement life)
|
The physical improvement to the soil’s mechanical behavior makes geosynthetics valuable in roadway and pavement design applications. Principally, the use of products like geogrids, and geocells means that the soil is confined and its mechanical properties are affected. Their impact varies depending on the layer in which they are used and the specific type of geosynthetic.
Economic efficiency: Geosynthetics are often more economical than traditional methods which rely on thicker pavements or extensive drainage systems. By reducing the need for materials, site logistics, and inexpensive labour costs, Strata Global can impact construction costs by as much as 35%.
Faster construction: Easy installation of geosynthetics reduces construction time and traffic disruptions, leading to cost savings since it arrives in customizable sizes of rolls, for length and width both.
Pavement design is an important aspect of construction –whether it’s national highways, state roads, or for borders. There are conditions to consider –which affect how thick the road should be, temperature profiles, freeze-thaw cycles, and a lot more affect the design itself. While the list below is not exhaustive, it provides an indicative guide into the factors. Other aspects that should influence decision making would include stress analysis, moisture content of the materials, traffic and loading, drainage and hydraulics among a wider list of details.
Any successful application of geosynthetics in roadway and pavement construction must consider the various factors presented. Engineers and contractors need to know the project objective, subgrade conditions, pavement structure, type, properties of geosynthetics, ways of installation, and long-term performance aspects to make proper decisions that enhance the performance and durability of their projects.
The many benefits of geosynthetics include enhanced stability, drainage, erosion control, and reinforcement. These can be attained by selecting appropriate geosynthetics and proper installation techniques.
It cannot be generalized that the application of geosynthetics is single, as one size suits all. Requirements regarding the kind of geosynthetic and its placement are completely dependent on particular projects. All factors considered, engineers and contractors could ensure that geosynthetics are undertaken successfully for each roadway and pavement construction project.
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Director, President – Glen Raven Technical Fabrics
Strata/Glen Raven tenure: 10 years/28 years
Total industry experience: 35 years
MBA – Wake Forest University
Directs the strategic direction of Glen Raven’s automotive, protective apparel, military, geogrid, outdoor and logistic businesses.
Director, General Manager, Strata Inc.
Strata/Strata Inc. tenure: 3 years/14 years
Total industry experience: 25 years
MBA – Georgia State University
Led the integration of Strata Inc. business operations into the headquarters of GRTF and transition from USA based to India based manufacturing.
Director
Strata tenure: 17 years
Total industry experience: 47 years
CA – ICA
Played a key role in the establishment of Strata’s India operations. Provides vision for product innovation and leveraging new technology trends.
Global Technical Sales Director
Strata tenure: 7 years
Total industry experience: 32 years
Civil & Geotechnical Engineer (First class)
Provides highly technical and innovative civil engineering solutions in India and around the world. Responsible for the design and execution of large-scale geotechnical projects around the world including Australia, Asia, Europe, Africa, Middle East, and South America.
CTO – Chief Technology Officer
Strata tenure: 9 years
Total industry experience: 48 years
BTech (Hons), MTech (Civil) Both IIT Bombay, DMS (Bombay University), FIE, FIGS, Chartered Engineer
Streamlines the designs of Geosynthetics and has brought innovation in geogrid and geocell design application.
COO – Projects and Sales
Strata tenure: 13 years
Total industry experience: 24 years
MBA – University of Gujarat
Leads the monetization of products and solutions while ensuring highest execution quality and project profitability.
COO – Technical Textiles
Strata tenure: 13 years
Total industry experience: 33 years
BE (Mechanical) – Nagpur University
Drives excellence in process design, product features and cost effectiveness in production.
CFO – Chief Financial Officer
Strata tenure: 8 years
Total industry experience: 35 years
CA – ICA, ICWA – ICWAI
Leads the finance, accounting, taxation, commercial, legal and IT functions and assisting on all strategic and operational matters.
CDO – Chief Development Officer
Strata tenure: 10 years
Total industry experience: 13 years
MBA – ISB, Hyderabad
Leads diversification of the product portfolio, monetizing the new products and ensuring successful sustained financial growth of the company top line.
CEO – Chief Executive Officer
Strata tenure: 14 years
Total industry experience: 42 years
B Tech (Chemical) – IIT Delhi
Leads day-to-day business operations of the company with focus on capacity expansion, product and process improvement.
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