What's The Difference Between Geogrid and Geocells?

Although there are several geosynthetic products for ground reinforcement, geocells and geogrids are used most extensively. Before choosing one, you need to know how they differ and what applications they are suited for.

The differences between geocells and geogrids include their shapes, the degree of flexibility they provide, and their relative load-bearing capacities. Both have similar ground and roadway support applications, geocells are more suited for soft subgrades than geogrids. Geogrids are also used in the construction of retaining walls in addition to roads, driveways, and parking lots.

The difference between geocells and geogrid article picture

In this article, we will point out the main differences between geocells and geogrids. We will also explain the applications they are suited for and when they should not be used. Additionally, we will list the general steps to install both the products at the end of the article.

Geocells vs. Geogrids

Although both are similar geosynthetic products, geocells and geogrids differ based on their shape, lateral restriction and stiffness, and load-bearing capacity. Read on to find out more about the differences.

Shape

The geocell is a deep, three-dimensional mesh structure, while the geogrid is typically two-dimensional. Geocells interlock to resemble a honeycomb-like structure. As the name suggests, geogrids resemble a tight grid.

Lateral Restriction and Stiffness

The 2D structure of geogrids makes them more flexible than geocells and ideal for use in instances where a flexible top support or a separator is needed. A geogrid is a flatter, tighter structure that inhibits adjustability more so than a geocell.

Load-Bearing Capacity

The 3D structure and the vertical support of each cell give geocells superior load-bearing capacity. Geocells are less likely to bend, buckle, and sink into the subgrade over time. Furthermore, almost any infill material can be used with geocells. The relatively flat nature of geogrids restricts the type of infill you can use with this product.

What Applications Are Each Product Best Suited For?

Geocells and geogrids are two types of geosynthetic products. These are synthetic products used in civil engineering projects to stabilize terrains like slopes and erosion-prone soils.

These products are typically made from polymers and are used extensively in artificial earth-supported projects, systems, and structures that demand high durability.

Geogrids and geocells are best suited for constructing earth-retaining and earth-supported structures like steep slopes and mechanically stabilized earth (MSE) retaining walls.

These structures need to be durable, withstand vertical or lateral pressure, and provide support for other structural components.

They are used in construction work because:

They have excellent T ensile Strength
Are designed to distribute load evenly across a large surface area.
Reduce costs by preventing cracking, spalling, corrosion, and splintering, common in conventional earth-retention projects.
Do away with the need for using expensive piling or over-excavating methods on poor subgrades.
Are easy to install, unlike sand, gravel, and clay which need to be transported using heavy earth-moving machinery.

Applications Geocell Are Best Suited For

Geocells are best suited for the following applications

Roadway projects
Soil foundations
Retaining walls
Slope stabilization
Reinforcement for structural elements
Drainage and filtration
Landfill and environmental barrier

Geocells make it possible to use locally-available, cheap, and even poorly-graded and inferior aggregates. For instance, local native soils, quarry waste, and recycled materials can be used as infill.

This reduces the overall cost of projects and benefits the environment by keeping waste products away from landfills.

Geogrids can reinforce shallow foundations by increasing the load-bearing capacity. Both uniaxial and bi-axial geogrids are used to stabilize the soil below a shallow foundation. Geogrids are easy to install and are ideal for such applications where the structural load is distributed between the foundation and the reinforcement layer.

Geocell installed on a roadway

Roadway Projects

Geocells are used in roadway projects like:

Roads
Pavements when reduced thickness is desired
Access lanes
Railroads
Parking lots
Runways

What do Geocells do for Roadways?

Improve subgrade
Reinforce base and surface courses
Prevent displacement of railway ballast
Reduce lateral movement of the aggregate
Reduce soil settlement
Increase load-bearing capacity
Distribute the load
Reduce the amount of aggregate required over the years to extend the service life of roads

Drainage and Filtration

Landfill and Environmental Barrier

Geogrids are used to build waste landfill retaining walls to protect the surrounding environment. The watertight membrane prevents toxic, chemical waste from leaching into adjacent water bodies and seeping into the soil nearby.

Geogrids have similar applications like geocells. However, they are not substitutes for one another in all situations. The choice of a reinforcement depends on the strength and stability of the subgrade and the traffic or the load the surface will bear. So, it helps to know what applications each product is not suited to.

How Are Geocells and Geogrids Installed?

Geocells and geogrids should be installed according to the manufacturer’s instructions on the packaging and after consulting a geotechnical engineer. An engineer verifies whether the subgrade and the elevation are suitable for installing a geosynthetic product.

Read on to find out how to install geocells and geogrids.

Installing Geocells

The following components are needed for installing geocells:

Anchoring pins to stake or hold in place the panels.
Locks or staples to secure adjacent panels.
The requisite number of geogrid or geocell panels as determined by an engineer.
A small compressor (100 PSI) and a generator if staples are used to join the panels.

The following are the steps of installing geocells:

Preparing the Subgrade

The project determines if the subgrade may need to be prepared before installing geocells. For instance, concrete may be poured into the subgrade as an added reinforcement. Preparing the subgrade ensures that you are installing geocells efficiently.

Installing a Non-Woven Geotextile Fabric

This is an optional step. An engineer is the best person to determine if you need to install a non-woven geotextile or a geomembrane liner.

The geotextile is placed over the soil and fixed in place. A second geotextile liner can be used to protect the first one.

The geomembrane liner acts as a barrier between the panels and the soil and prevents the panels from sinking into the soil.

Expanding the Panels

It is wise to expand single panels to get an idea about how many panels you need to expand. This saves time and effort down the line.

Keep the following pointers in mind when expanding the panels:

Reach the entire length of expansion to ensure proper coverage and the highest yield.
Use sandbags or a stretcher frame to expand the panels.
You can use clips to secure the panels in place of stakes.
Pull the edges of the panels after they have reached their full length to ensure they take their rectangular shapes.

Joining the Panels

You may join the panels before expanding to increase the rate of installation. However, the more the number of panels you join, the larger the crew you need to deploy. You can join the panels using a pneumatic stapler and staples or locks. You need a compressor and a generator for stapling.

You can join the panels using a pneumatic stapler and staples or locks. You need a compressor and a generator for stapling.

Filling the Panels

You may need to build a temporary dirt ramp to let the trucks get on top of the expanded panels to dump a full load of fill material. An excavator then pushes the fill material onto the empty cells.

While filling, ensure that the bucket is as close to the empty cells as possible. This minimizes the drop height and avoids damaging or displacing the panels. You can pull out the stakes or the sandbags after the cells are filled and reuse them for other panels.

Compacting the Fill Material

A vibratory roller compacts the fill material. These compactors can be found in most big box home improvement stores for rental.

Installing Geogrid

The following steps can be taken to install Geogrid

Prep and grade the soil
Lay and place the rolls
Anchor with pins
Cover grid with aggregate fill
Compact the fill aggregate

Prep and grade the soil

You need to smooth any rut on the subgrade and compact the soil before installing. Ensure no sharp objects or debris are lying on the coverage area that may damage the grid. When the ground is properly prepared, it will be much easier for you to install the geogrid.

Lay and place the rolls

Ensure no sharp objects or debris are lying on the coverage area that may damage the grid. When the ground is properly prepared, it will be much easier for you to install the geogrid. After rolling it out, the geogrid fabric should be tensioned by hand until it is tight, free of wrinkles, and laying flat. Adjacent geogrid rolls may be butted together side-by-side without overlap. Splices in the main reinforcement direction should be avoided.

Ensure that the grid is weighed down and held in place by U-staples or zip ties. You can also mound small piles of the fill to keep the grid in place.

Anchor with pins

Here’s how you can anchor the geogrid rolls:

Unroll the geogrid partially
Align it
Pull it taut and smoothen wrinkles and remove laydown slack
Cover grid with aggregate fill
Compact the fill aggregate

Cover grid with aggregate fill

Keep the following pointers in mind while dumping and spreading the aggregate fill:

The thickness of the fill should be at least six inches and more if the subgrade is soft.
If the subgrade is not soft, standard, highway-legal trucks with rubber tires can drive over the geogrid at very slow speeds (less than 5 mph or 8.04 km/h) to dump the aggregate fill.
For soft subgrades, back the truck up and dump the fill over the previously placed fill.
Use a lightweight, low ground pressure dozer to spread the fill over the empty geogrid.
The fill should gently cascade into the empty geogrid instead of being pushed into it.

Geogrid before aggerate fill

Compact the fill aggregate

Use a vibratory roller to pack in the fill. However, use a light roller if the soil is soft. Check that the moisture level of the fill material is as close to optimum as possible. This ensures the compaction is adequate. You can spray water while compacting sand fill.

Conclusion

Geocells and geogrids look vastly different but have only marginally different characteristics. So, both can be used for similar applications. A geotechnical engineer is the best person to determine which one of these two products is most suited for your project. The decision to use one and not the other depends on factors like the quality of the soil and how much load the reinforcement structure needs to withstand.