Geogrid For Retaining Walls
Installing geogrid during the construction of a retaining wall is simple and can add a great deal of longevity. Before beginning any excavation be sure to call 811 to have your site surveyed and locate any existing utilities.
When grid is needed depends on both the wall height and the soils being retained. The most cantankerous and least cooperative soils (such as clay) require a very robust retaining system.
1. Strength
The most obvious benefit of geogrid for retaining walls is its strength. It increases the friction angle of your soil cylinder which can help reduce lateral deflections and settlement of the wall, and it adds considerable strength to your backfill materials.
Uniaxial geogrids are most commonly used in structural applications like retaining walls. They are easy to install and pinned in place with the next course of blocks making them an efficient way to retain soil. They are also relatively low cost and can be easily recycled or reused.
The type and length of geogrid needed varies with each wall project depending on wall height, surcharge loading, slopes and soil conditions. Always consult a qualified professional civil engineer licensed in your state for final wall design details and recommendations.
2. Stability
The primary function of geogrid is to increase the load-bearing capacity of the soil behind retaining walls. This is achieved by distributing forces over a larger area which reduces stress on individual wall elements.
The tensile strength of the geogrid helps hold the soil mass together, increasing the internal size of the reinforced soil and preventing local failure of the soil wedge or lateral facing deflections of the wall. The increase in size also allows for a higher surcharge loading without causing block movement or failure.
Most retaining wall projects will require at least one layer of geogrid. For more extreme applications, including heavy surcharge loading or taller walls, an engineer should be consulted to review the design and provide recommendations.
Cut the stabilizing landscape geogrid (rated for retaining walls) from Geogrid Manufacturers the roll to a specific length for proper installation, following the manufacturer’s criteria and final wall design plans. Install the VERSA-Grid over the properly compacted backfill, drainage aggregate and inserted VERSA-LOK units. VERSA-Grid should be laid so that the front edge is one inch behind the wall face.
3. Drainage
It may be obvious to some, but geogrids improve the strength of soils by providing a means for the soil particles to interlock with each other. This allows the ribs of the grid to distribute loads more evenly and prevent rutting, erosion or failure of the base material.
It also allows the soil to be “squeezed” together, providing a larger mass that resists lateral forces and surcharge loads much better than unreinforced soil. If a wall is designed for a high surcharge loading it is recommended to consult with a professional engineer to ensure the proper design and site conditions are achieved.
For those projects that do not require an engineer, a general rule of thumb is to place the geogrid in every second block layer, starting with the bottom course of blocks. For walls that are designed for higher lateral loads or surcharge loads it is recommended to add longer geogrid lengths in the top row of blocks. Once placed, backfill the Reinforced Zone with a minimum of 6 inches of reinforcement fill cover before driving or turning any equipment over the grid to prevent excessive damage to the grid and wall units.
4. Durability
In the same way that a sturdy tent supports its structure and keeps out rain, geogrid strengthens and stabilizes soil structures like retaining walls. It reduces the occurrence of settlement, wall movement and overall failure by spreading concentrated loading across a greater area.
The amount of stabilizing grid needed depends not only on the material used to construct the retaining wall but also the type of soil being retained. Clay soils, which are common throughout Appleton, Neenah and the Fox Cities, are among the most cantankerous and least cooperative soils there are to work with. They resist compaction and hold onto moisture causing them to swell when wet and shrink when dry.
Stabilizing grid helps the clay soils used in retaining walls to act more cohesively as one mass, making for much stronger Biaxial tensile geogrid and more stable walls. When using geogrid, place a minimum of 6 inches of backfill over it before driving or turning any equipment over the grid to avoid excessive damage. There are several different types of geogrids available and the type chosen is determined by what kind of loading the retaining wall will experience. For retaining walls that will have mostly load perpendicular to the wall, a uniaxial geogrid should be used.
5. Safety
Retaining walls can withstand more soil pressure when geogrid is included. This allows the construction of taller and steeper walls without having to worry about the potential for movement or failure. The grid-like structure of geogrids prevents soil from moving behind the wall, making it easier and safer to build in tight spaces.
Load-bearing reinforced soil walls reduce construction costs, can halve build times and work with a wide range of materials, including site-won fill. This also means that more valuable land can be reclaimed for development.
For the best results, install a drainage blanket under your blocks and cut sections of geogrid to the length specified in the approved plans. Ensure that the thick or stiff ribs in the geogrid are perpendicular to the block layer. This is the best way to ensure that the geogrid is pinned to place. Continue with this procedure every other block layer until you reach your desired height of retaining wall.