How to Install Geogrid Biaxial Mesh for Clay Ground and Paving Stability
Geogrid, also known as georgic or biaxial mesh, is a geosynthetic material with a grid-like structure (see figure). It is often used for soil reinforcement, stabilisation, and behind retaining walls.
In paving applications, geogrids are embedded within or beneath the sub-base or base layers of the pavement to improve its overall structural performance — noting that geogrid can also be installed in the bedding mortar or laying course.
Using geogrid for paving on clay ground is an effective way to improve the stability and load-bearing capacity of the pavement.
Clay soils are renowned for their poor drainage and susceptibility to movement, which can lead to issues such as sinking, cracking, and generally uneven surfaces. Incorporating a geogrid into the pavement structure can help mitigate these problems.
Additional benefits of using geogrid include the ability to reduce the required depth of both the base and sub-base, particularly on poor subgrades with low CBR (California Bearing Ratio) readings. This reduction in depth is better for the environment in terms of lower spoil removal to landfill and reduced aggregate usage.
Geogrid also helps distribute loads more evenly, especially when installed in layers. This is particularly important on clay subgrades, which can deform, expand, or contract significantly depending on moisture content.
Installation Guide
- Determine and outline the boundaries of the designated area for paving and mark it out, making sure it corresponds with the planned design. “Measure twice, cut once” is the all-important phrase during the early stages of setting out a project.
- Excavate/reduce dig the area to the required depth, taking into account the full build-up of the pavement structure — including the subgrade, sub-base, base, geogrid, laying course, and surface course.
- Ensure the subgrade is sufficiently compacted and graded to the same fall as the surface course. Any soft spots should be dug deeper and filled with lean mix concrete or compacted MOT Type 1.
- If the subgrade has a low CBR and a capping layer is required, the geogrid can be laid on top of the compacted capping layer rather than directly on the subgrade.
- When laying a driveway, position the geogrid perpendicular to the direction of traffic or the car’s exit and entrance.
- If multiple rolls of geogrid are required, overlap the adjacent rolls by a minimum of 300mm. This ensures continuous reinforcement across the area. Joints should be secured using pins (provided by the supplier) and/or cable ties every 50–100mm, depending on the manufacturer’s guidance.
- Ensure there are no ripples in the geogrid before beginning to lay your sub-base or base aggregates. Compact in layers until you reach your required compacted depth. Again, check that your base has the same fall as the intended surface course. This will ensure an even depth of laying course material and consistent compaction.
- An alkali-resistant geogrid can also be installed into the laying course or mortar bed. This further reduces the chances of surface course failure.
- Install the laying course and surface course.
