What is the primary function of geogrids in pavements?

To provide reinforcement and confinement to unbound aggregate layers, which improves load distribution, reduces rutting, and can extend pavement life or reduce layer thickness (Clause 5).

What is the minimum recommended aggregate cover over a geogrid?

A minimum compacted thickness of 150 mm of aggregate should be placed over the geogrid before allowing heavy construction traffic (Clause 7.2.3).

How much should geogrid rolls be overlapped?

Overlap depends on subgrade strength. For subgrade CBR > 3, overlap should be 300 mm. For CBR < 3, overlap should be 600 mm to 1000 mm (Clause 7.2.2).

What is a key material property for geogrids in reinforcement applications?

Tensile strength at a low strain (e.g., 2% or 5%) is crucial, as large deformations are unacceptable in a pavement structure (Table 1).

IS 14792

: 2000

Use of Geogrids in Permanent Pavement - Guidelines

CurrentSpecializedGuidelinesTransportation · Roads and Pavement

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This standard provides guidelines for the use of geogrids to reinforce unbound layers in flexible and rigid pavements. It covers material specifications, functions, design considerations, and construction methods to improve pavement performance and service life by enhancing the structural capacity of pavement layers.

Provides guidelines for the design and construction of permanent flexible pavements incorporating geogrids for reinforcement and improved performance.

Quick Reference Values

Minimum compacted cover over geogrid150 mm

Typical overlap for geogrid rolls (Subgrade CBR > 3)300 mm

Typical overlap for geogrid rolls (Subgrade CBR < 3)600 mm

Minimum junction efficiency for biaxial geogrids90 %

Key design property for reinforcementTensile strength at 2% strain

Key Formulas

TBR = N_r / N_u — Traffic Benefit Ratio, where N_r is number of load repetitions with reinforcement and N_u is without reinforcement.

Practical Notes

Ensure geogrid is laid flat and pre-tensioned to remove slack before placing aggregate to maximize reinforcement effect.

The choice of fill material is critical; avoid sharp, large aggregates that could damage the geogrid during compaction.

Design is often based on empirical methods like the Giroud-Han method (Annex A) which calculates a Traffic Benefit Ratio (TBR) to quantify the benefit.