Quality gabion baskets require quality rock infill. We can offer suitable rock supply depending on the site for Gabion installation, often the rock supplier does not have rock stockpiled and we do try to provide the necessary information for obtaining the material. We also offer expert advice regarding the best rock specifications for your particular requirement.
The rock we recommend must be un-weathered and solid without flaking or weathering evident. The correct size to be used must be 100-250 mm minimum size for gabions (1m high baskets). With river mattresses the rock size is also 100-2/3 the mattress thickness so that at least two layers of rock can be used in the mattress layer thickness. Small rock fragments must not be used on the surface of either gabions or mattresses in river course situations as the fine material will be removed in high water flows. Always check that the rock size is bigger than the hexagonal mesh opening, within the centre of a gabion basket smaller rock may be used and limited to the centre of the gabion only.
Soft rocks and brick fragments are not suitable due to its capacity to absorb water and soften over time, flat rock is usually not adequate as it does not provide for the same mechanical interlock in the gabion provided by blasted angular rock, rounded river rock is ok, however is does harm the environment after removal and it is more difficult to obtain a flat gabion facing.
Usually the rock density should be a minimum of 2.6 tons/m3, with an average void ratio of 35%(also allowing 35% for waste/fines) we generally recommend about 2 tons of rock per m3. The rock should be placed as close to the packing position when offloaded from the truck to reduce double handling of this resource on sites. With experience gained we have found that labor can pack 1-3m3 per man per day, to be conservative we generally allow for 1 man/m3/day. The rock and labor prices normally amount to approximately 33% each of the final completed gabion cost, the other 33% is made up from the galvanised gabion, with PVC coated baskets, we allow about 20% to the overall cost.