Geogrid Fabric for Retaining Walls

Geogrid, also known as retaining wall mesh, is primarily used to distribute concentrated loads over wider areas. It is commonly used under footings, roadways, and other regions requiring subgrade support. Another significant application is in reinforcing retaining walls. For homeowners or builders considering geogrid, it is a worthwhile investment. It is relatively inexpensive and significantly enhances the strength of driveways, patios, and subgrades.

Types of Geogrid

The most common types of geogrid are uniaxial, biaxial, and triaxial grids. The choice of the grid depends on the type of loading the soil will encounter. For retaining walls, where the primary load is perpendicular to the wall face, uniaxial grids (or multi-directional grids for shorter walls) are typically used. For roadways and parking lots, where the load can come from any direction, biaxial or triaxial grids are more suitable.

How Does Geogrid Work?

Geogrid functions by spreading concentrated loads from vehicles or footings over a wider area, thereby reducing settlement and movement. This principle is simple, though its explanation can be more complex.

Consider a box filled with loose sand: pressing your hands into the sand will make them sink until the sand particles rub against each other and resist further movement. This resistance occurs due to the friction between the particles.

In construction, the soil beneath roads, footings, or foundations can move, causing settlement. Geotechnical engineers mitigate this issue using geogrid. Geogrid interlocks with the sand particles, providing tensile resistance stronger than the sand’s frictional resistance. This spreads the load across a larger area, reducing pressure on the soil below and movement above the grid, thereby enhancing the soil’s strength and stability.

Uniaxial Geogrid in Retaining Walls

Uniaxial geogrid is commonly used in retaining walls. Unlike biaxial or triaxial grids, uniaxial geogrid is loaded in one direction along its stronger axis. It does not control settlement but serves as an anchor. The stronger axis is thicker and stiffer than the fabric or thread holding the grid together, which is crucial for the grid’s performance in retaining walls.

In retaining wall construction, uniaxial geogrid uses the soil’s weight to support the wall by anchoring it to the soil. This integration causes the retained soil to act as a single mass with the wall, holding back unreinforced soil from behind. The grid is placed on top of the block section and pinned by the next course of blocks, ensuring the strong axis runs crosswise to the wall face. The backfill material is then compacted at the wall’s end to increase tension.

Importance of Proper Geogrid Installation

Proper installation of geogrid is critical. The reinforced soil, when compacted, pulls back on the retaining wall blocks, helping to hold the wall up as a reinforced structure. This interlocking of retained soil and blocks allows the entire mass to resist unreinforced soil. Geogrid placement, lengths, and types are specified in design packages and inspected during construction to ensure compliance with specifications.

Visual Examples

• Side View of Geogrid for a Retaining Wall: A diagram illustrating the proper placement of geogrid in retaining wall construction.
• Example of Poorly Constructed Retaining Wall: An image showing the consequences of improper geogrid installation.

Using geogrid effectively can prevent issues with retaining walls, ensuring they remain sturdy and intact over time.