WHAT IS GEOGRID?
Geogrid is a manufactured high strength reinforcement grid that comes in rolls of various sizes and strengths. It is composed of high-molecular weight, high-tenacity multi-filament polyester yarns that are woven together into a stable mesh.
WHAT ARE THE ADVANTAGES OF GEOGRID?
- Adds strength and longevity to your wall
- Helps prevent wall failure
- Resistant to biological degradation and naturally encountered chemicals, alkalis and acids.
WHERE CAN GEOGRID BE USED?
- Retaining walls
- Steep Slopes/Embankments
- Sub-grade Stabilization
- Waste Containment
- Void Bridging
TYPES OF GEOGRID:
Geogrids are made as either bi-directional (bi axial) or uni-directional (uni axial).
Bi-directional geogrid has significant tensile strength in both directions. This structure also provides an ideal interlocking system for more effective force bearing and diffusion in soil. Some examples of bi-directional geogrid are the 3 Series and Universal Geogrid from SRW Products.
Tip: Bi-directional geogrid should be rolled out perpendicular or parallel to the wall.
Uni-directional geogrid have very high tensile strength and high stiffness in the machine direction with very low stiffness in the other direction. Uni directional geogrids provide stability and are often used in applications that has little to no loading in the secondary direction. Some examples of uni-directional geogrids are the 5 to 10 Series geogrids from SRW Products.
Tip: Uni-directional geogrid should ALWAYS be rolled out perpendicular to the wall.
This structure has a very high tensile strength. The tensile strength of the product can adapt to a variety of soil, is widely used reinforced reinforcement materials.
WHY IS GEOGRID IN RETAINING WALLS SO IMPORTANT?
The soil behind retaining walls can exert a tremendous amount of pressure on the blocks so it is very crucial to use a high quality geogrid (such as one from SRW Porducts) in-between the blocks to help alleviate that pressure and keep the wall from falling over.
To better visualize how geogrid works think of yourself leaning over. Now imagine someone standing behind you and holding your shirt so that you don’t completely fall over. You are acting as the retaining wall, your shirt is acting as the geogrid, and the person holding your shirt from behind is acting as the Earth. Without the geogrid there would be nothing for the Earth “to grab” and keep the wall from tumbling over.
Geogrid also creates a reinforced coherent mass behind the retaining wall by stabilizing the soil.
To see just how well geogrid reinforces soil check out this one minute demonstration by Allan Block.
The test performed takes two cylinders of soil and applies vertical force to see how the soil performs. The first cylinder is just compacted material. The second is also compacted material with the addition of mesh screens to simulate the use of geogrid reinforcement.
Notice in the video how the geogrid reinforces the soil mass so that it can withstand much more force. It also helps the soil that is reinforced to act as one coherent gravity mass. If you consider a simple gravity retaining wall, the forces from the soil being retained must be retained by the mass of the wall blocks.
When you use geogrid with a retaining wall, the mass of the blocks and the additional mass of the reinforced soil helps to withstand the pressures behind the wall. This combined mass is what allows very tall walls to be built when using geogrid.
To use geogrid in a retaining wall first follow the installation instructions supplied with the retaining wall of your choice., This includes foundation preparation, block alignment, core filling, drainage rock placement, back fill placement, and compaction. For a brief how to please check out our article on How to Build a Block Retaining Wall.
- Start the geogrid near the face of the block and roll out in one continuous piece to the back of the reinforced soil mass (no splicing). Butt together at edges — DO NOT OVERLAP GEOGRID.
Tip: SRW Universal and 3 Series geogrid are bi-directional and can be rolled out either perpendicular or parallel to the wall.
2. Install geogrid under tension. Be sure to remove any slack by pulling the grid backwards from the wall face. A nominal tension can be maintained by staples or stakes, until the geogrid has been covered by at least 6 inches of structural fill.
3. Place the next course of block on top of the geogrid. Back fill and compact the soil.
Tip: Always back fill and compact one course of block at a time. Keep an adequate cushion of soil between the geogrid and equipment.
4. Repeat process until retaining wall is completed.
TLC Supply in Quincy, MA is your #1 place to purchase Geogrid for your retaining wall project. We carry several high quality Bi-Directional and Uni-Directional Geogrid reinforcements from industry leader SRW Products.
We are happy to answer any of your project questions, just leave a comment below!
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