How are gravel stabilisation grids installed to form a sub-base?

Gravel stabilisation grids can be installed in three ways, depending on the ground conditions. They may be laid directly on the prepared formation over firm existing ground, set in a bed of angular crushed grit on the formation, or placed above a compacted crushed stone sub-base. In every case, the cells are filled completely with angular crushed grit and struck off flush with the top edges of the grids.

For firm ground subject to light use, the grids are laid directly on the formation. The topsoil is removed and the formation is prepared carefully before the grid units are positioned. Their 4 cm ground spikes penetrate the soil beneath.

Where minor irregularities need to be levelled, a thin bed of angular crushed grit is placed on the formation. This layer should be about 2 to 5 cm deep. The grids are set into the grit so that the ground spikes pass through the layer and enter the soil below.

If the ground is less firm, a frost-resistant build-up is required or heavier use is expected, a crushed stone sub-base is built up and compacted in layers. The ground spikes cannot penetrate the compacted crushed stone. A layer of angular crushed grit at least 6 cm deep is therefore placed over the sub-base, allowing the spikes to be fully embedded in the grit and the grids to be fully bedded.