Geogrid: Types, Functions, Importance and Applications

Last Updated on 21/04/2021

Geogrid: Types, Functions, Importance and Applications

Mashood Ahmed
School Of Textile and Design (STD)
University of Management & Technology, Lahore, Pakistan.
Email: 111811008@umt.edu.pk

Introduction:
A geogrid is geosynthetic material used to reinforce soils and similar materials. Geogrids are commonly used to reinforce retaining walls, as well as subcases or subsoil below roads or structures. Soils pull apart under tension. Compared to soil, geogrids are strong in tension. This fact allows them to transfer forces to a larger area of soil than would otherwise be the case.

Geogrids are commonly made polymer materials, such as polyester, polyethylene or polyproylene. They may be wovern or knitted from yarns, heat-welded from strips of material or produced by punching a regular pattern of holes in sheets of material, then stretched into a grid.

Geogrid products are designed for reinforcement and, characteristically, are integrally connected to elements separated by in-plane apertures.

Geogrids form a distinct category of geosynthetics designed for reinforcement. These products are characterized by a relatively high tensile strength and a uniformly distributed array of large apertures (openings between the longitudinal and transverse elements). The apertures allow soil particles on either side of the installed sheet to come into direct contact, thereby increasing the interaction between the geogrid and some soils. Also, the apertures ensure vertical drainage of a reinforced free-draining soil.

The geogrid elements vary in polymer type and cross-sectional dimensions. They can sometimes change shape and dimensions within their length. Geogrids are either integrally manufactured, ultrasonically or adhesive bonded, or joined in a knitting or weaving process and then coated.

Although geogrids are used primarily for reinforcement, some products are designed for asphalt overlay and waterproofing or for separation and stabilization. Geogrids also are used as gabions and sheet anchors, inserted between geotextiles and geomembranes, or used to construct mattresses for fills or embankments over soft soils.

Geotextile vs Geogrid:

Geotextiles:
Watersaver provides civil and environmental nonwoven geotextiles with excellent dimensional stability. Watersaver provided geotextile products are resistant to ultraviolet deterioration, rotting, biological degradation and naturally encountered basics and acids. Geotextiles can be utilized for separation and filtration. Non-woven, woven and high strength fabrics are all available.

Geogrids:
Watersaver provided geogrid products increase efficiency and minimize maintenance on roads, entrances, laydown areas and Oil & Gas pad sites. By utilizing BX geogrids, reduction in aggregate thickness can be achieved. Engineering is available for aggregate reduction.

Categories of Geogrid:
Currently there are three categories of geogrids. The first, and original, geogrids (called unitized or homogeneous types, or more commonly referred to as ‘punched and drawn geogrids’) were invented by Dr Frank Brian Mercer in the United Kingdom at Netlon, Ltd, and were brought in 1982 to North America by the Tensar Corporation. A conference in 1984 was helpful in bringing geogrids to the engineering design community. A similar type of drawn geogrid which originated in Italy by Tenax is also available, as are products by new manufacturers in Asia.

The second category of geogrids are more flexible, textile-like geogrids using bundles of polyethylene-coated polyesterfibres as the reinforcing component. They were first developed by ICI Linear Composites LTD in the United Kingdom around 1980. This led to the development of polyester yarn geogrids made on textile weaving machinery. In this process hundreds of continuous fibers are gathered together to form yarns which are woven into longitudinal and transverse ribs with large open spaces between. The cross-overs are joined by knitting or intertwining before the entire unit is protected by a subsequent coating. Bitumen, latex, or PVCare the usual coating materials. Geosynthetics within this group are manufactured by many companies having various trademarked products. There are possibly as many as 25 companies manufacturing coated yarn-type polyester geogrids on a worldwide basis.

The third category of geogrids is made by laser or ultrasonically bonding together polyester or polypropylene rods or straps in a grid like pattern. Two manufacturers currently make such geogrids.

The geogrid sector is extremely active not only in manufacturing new products, but also in providing significant technical information to aid the design engineer

Importance of Geogrid:

• Geogrids improve the structural integrity of soils in roadways, walls and slopes by reinforcing and confining fill materials and distributing load forces. Geogrids are the answer for designers, developers and contractors facing the challenges posed by sloping ground and soft subgrades.
• Geogrids help soils stand at virtually any desired angle in grade separation applications. In retaining wall and slope applications, geogrids can be combined with a wide variety of facing elements to produce the desired aesthetics for any project.
• Geogrids provide support for the construction of access roads, highways, berms, dikes and structure applications that previously required the use of expensive over-excavating or piling methods on weak subgrades. Geogrids are also used in base reinforcement applications to reduce aggregate thickness requirements or extend roadway performance life.

Types of Geogrid:
There are different types of geogrid. Among them biaxial and uniaxial geogrids are widely used. TriAx geogrid is also used.

A. Biaxial Geogrids
Biaxial Geogrids improve the structural integrity of roadways by confining and distributing load forces. Geogrids provide support for the construction of access roads, highways and applications on weak subgrades that previously required expensive over-excavating and replacing. Geogrids are also used for road construction on stable subgrades to reduce aggregate thickness requirements and/or extend roadway performance life.

Base Reinforcement
When building permanent roads on a relatively firm foundation, Biaxial Geogrids provide enhanced performance or reduction of the road structure thickness. Geogrids change the way the base course performs under load. With their open grid structure and high tensile modulus, they interact with and confine base course materials, much like a rack confines balls in the game of pool.

Subgrade Improvement
When weak subgrade conditions are encountered Biaxial Geogrids are used to provide a temporary road surface or a stable foundation for a permanent road. Biaxial Geogrids work much like a snowshoe to distribute loads over a wider area.

Applications

• Roads
• MSE

B. Uniaxial Geogrids
In grade separation applications, Uniaxial Geogrids are used to help soils stand at virtually any desired angle; from 0 to 90 degrees. Geogrids can be combined with a wide variety of facing elements in retaining wall and slope applications to produce the desired structural or aesthetic conditions for any project.

Geogrid Reinforced Soil Retaining Walls
Geogrid reinforced soil retaining walls offer economical and aesthetically pleasing alternatives to conventional retaining wall systems. The geogrid reinforced fill zone behind the wall facing acts as a uniform mass or block, providing stability to the wall and structure. Geogrids work with a wide variety of fill materials and facing elements including segmental concrete blocks, concrete panels, geogrid wraps, timbers or boulders.

Geogrid Reinforced Slopes
Geogrid reinforced slopes provide a natural and economical alternative to conventional concrete retaining walls. Geogrid reinforced slopes create naturally finished slope structures that are easy to construct and enhance property values because of their natural beauty. Geogrid reinforced slopes can be built at any angle to provide the most economical use of available space while avoiding the increased cost of vertical structures.

The construction of embankments, bridge approach fills, dikes and causeways over soft soils and wetlands traditionally involves expensive, time consuming construction methods. Geogrid reinforcement of these structures minimizes the project footprint, fill requirements and differential settlement, saving time and money.

Applications

• MSE

C. TriAx Geogrids
TriAx is a revolutionary new geogrid product from Tensar. The triangular structure of TriAx geogrid, coupled with the increased rib thickness and junction efficiency, greatly improves aggregate interlock and confinement – leading to optimal structural performance of the mechanically stabilized layer.

Research indicates that TriAxgeogrid can reduce aggregate base/sub-base requirements by 25% to 50%.

TriAxgeogrid delivers performance in three dimensions:

• Multi-directional Load Distribution
• Triangular Aperture Geometry
• Junction Integrity and Efficiency
• Superior Performance for Paved and Unpaved Roads
• Less Stress on Subgrades
• Enhanced Snowshoe Effect

Spectra Roadway Improvement System
The Spectra System incorporates TriAxgeogrid as part of an engineered system that consists of technology, engineering, design, and products to create a mechanically stabilized pavement structure.

In combination with the Spectra System’s engineering and design services, cost-analysis tools and site assistance, TriAxgeogrid provides a simple, reliable, and affordable solution for constructing flexible pavements that deliver both reduced construction cost and long-term maintenance needs.

Geogrid Applications and Functions:

Applications:

• Retaining Walls
• Steepened Slopes
• Embankment Over Soft Soils
• Veneer Stability in Landfills
• Void Bridging
• Pavement Reinforcement

Functions:

1. Geogrid stabilize soil mass.
2. Creates a composite soil mass of increased strength
3. Geogrid is to soil what reinforcing steel is to concrete
4. Much higher loads can be carried by the soil structure

You may also like:

1. Different Important Functions of Geotextile
2. Application of Textile in Civil Engineering
3. Soil Improvement Techniques Using Geosynthetics

Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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