In the course of supporting steep slopes, aesthetical and environmental requirements must also be fulfilled besides technical requirements. Within a couple of years vegetation grows over gabion retaining walls, but selected plant species can also be planted in them in a planned way. Consequently their use offers numerous advantages as compared to other types of structures.
Flexibility: Subjected to alternating forces of tension and compression, the inherent flexibility of a gabion structure enables it to deform rather than break. This prevents loss of structural efficiency. Deforming in response to subsidence of foundation or internal stress is a functional feature, and rather than being a fault is in fact, a benefit.
Strength: Since gabions are bound together as a monolithic unit, the wire mesh is extremely strong under tension. The wire mesh shell is not simply a container for the stone filling, but a reinforcement of the entire structure. Additional strength is achieved by the use of vertical diaphragms. These diaphragms are affixed to the base of the gabions to restrict internal movement of the stone filling and provide further reinforcement. Gabion efficiency, rather than decreasing with age, actually increases. During early periods of use, silt and vegetation will collect within the rock filling to form a naturally permanent structure, enhancing the environment.
Permeability: Interstitial spaces in the stone fill within the baskets provide a great degree of permeability throughout the structure eliminating the need for a drainage system and preventing buildup of hydrostatic pressure which will displace and crack concrete structures. In river works, pressure and counterpressure on the banks due to variations in water depth between flood and low water are therefore also eliminated.
Economy: Wire mesh gabions are less expensive than most construction materials. Graded stone fill is usually locally available. Waste materials such as crushed concrete may be specified in place of stone.
Construction costs are reduced; unskilled laborers can easily learn to erect Modular Gabion Systems, fill them and close them properly. Many gabion structures may be built without any mechanical equipment. Pilings, underwater drainage systems and excavations are unnecessary. There's no need to drain the site or to construct a cofferdam for underwater installation. The first layer of gabions can be laid in water or in mud.
Upon completion, a gabion structure will take its full load immediately - without the waiting periods of up to one month normally associated with concrete structures. Gabion structures are virtually maintenance free.
Gabion boxes consist of elements of various sizes, which can be attached to each other to create the desired geometry. Gabion structures overgrown with vegetation suit the natural environment. The steel mesh surface can also be supplemented with wooden cover structures.
The mesh made of steel wire coated with a metal zinc-aluminium and, perhaps, a further plastic anti-corrosion layer may last as long as 120 years. A quality certificate has been issued for the products by the British quality control authority (BBA). The quality of the filling stone material is also an important aspect in respect of lifetime. Favourably eruptive, frost-resistant rocks should be used for filling the gabion boxes.
The price of gabion structures made of steel wire is more favourable than the price of other building materials. They are delivered flat-packed, therefore the costs of delivery are not significant. Trained workers can quickly learn how to assemble and fill the structures, therefore there is no need for a skilled labour force. In many cases the structures can be constructed without using machines. Generally pile driving, draining or the use of earth excavation machines can be avoided.
Gabion structures are characterised by great water permeability, so there is no need for constructing a back-drain system, which is essential in the case of concrete structures. On areas in contact with the soil geotextile fabric with high water permeability must be put down to stop the gaps between the stones from filling up.
In the case of water courses there is unhindered communication between ground water and the water flowing in the channel, no hydrostatic pressure is borne by the structure.
Due to the load bearing capacity of the steel mesh, the structure adapts flexibly to forces occurring as a result of soil movements occurring after the construction of the gabion wall (change of volume, sinking). Consequently the box made of steel mesh is not simply a box for accommodating stones, but it also strengthens the structure. The partition chambers (diaphragms) placed vertically in the box every meter also strengthen the structure. As years pass, the stems and roots of the vegetation growing over the structure strengthen the gabion structure even more.
The cost price of the retaining wall is 25-40% lower than that of retaining walls with a concrete structure.