Gabion
Gabion n., – a wire fabric container, uniformly partitioned, of variable size, interconnected with other similar containers and filled with stone at the site of use, to form flexible, permeable, monolithic structures such as retaining walls, sea walls, channel linings, revetements, weirs, etc. for erosion and flood control.
Gabion, are ‘caged rocks’, and they capture the feel of non-linearity, and essential characteristic of beauty in nature. It is the non-repetitive forms of the stone – a collection – a collection of individual fragments from the same geological time tied together by wire. Even the wire has a pattern that the rocks interfere with, leaving it structured yet random – no two cages remain visually the same.
Soil erosion is an ever present problem and gabions have proved to be a lasting civil engineering solution around the world.
The earliest known use of gabion-type structures was for bank protection along the Nile River about 7,000 years ago.
The gabion system has evolved from baskets of woven reeds to engineered containers manufactured from wire mesh. The lasting appeal of gabions lies in their inherent flexibility. Gabion structures yield to earth movement but maintain full efficiency and remain structurally sound. They are quite unlike rigid or semi-rigid structures which may suffer catastrophic failure when even slight changes occur in their foundations. They are a product of designing with nature.
Gabion construction has been used for many decades as free-draining retaining walls.
The wire baskets interlock, and the mass of the stone fill gives them some frictional strength. Gabion walls are traditionally battered – usually stepped using narrower baskets as the wall gets higher and higher.
The wire baskets can be made of many materials, although traditionally they are of galvanized or coated steel. There is little to inhibit the use of other materials such as bamboo slats or synthetic materials for the cage construction.
When gabion walls become very thick, it is sensible to consider a cellular form of construction.
One crucially important characteristic of any traditional gabion wall is its settlement. The stone fill will settle, and this implies a particular approach if the gabion wall is to be “tied” into the surrounding building fabric.
Relevant codes of practice include: BS 5390 – stones, hardness and weather resistance A974-97*– Standard Specification for Welded Wire Fabric Gabions and Gabion Mattresses *(ASTM)
Until 1992, when Ian Ritchie proposed using them as freestanding cantilevered walls for the Terrasson Cultural Greenhouse, their use had been associated with civil engineering projects for the retention of railway track ballast, and river banks.
The decision to use them was informed by the steeply sloping site, and the proposal to Kathryn Gustafson that they would be a sensible soil retention system for the new landscape. Since we were looking to harmonise the greenhouse with the landscape, it seemed appropriate to use gabion for the energy absorbing mass of the greenhouse walls, and to use evaporative cooling of the gabion surface in summer.
We investigated not only stone filled gabion baskets, but also earth and textile walls.
The use of indigenous, un-machined material drew upon investigations we had carried out in the late 80’s for a competition on the Isle of Aran in south west Scotland.
The quarry at St Yrieux was nearby Terrasson la-Villedieu on the Vésère river, and was the source material of the entire town centre’s construction The opportunity to create enclosure with minimum processing and transport was evident. The idea that the waste material from the quarry floor rather than quarrying new stone combined with an economic and basic technique associated with land stability and civil engineering could be the prime source of a new aesthetic in architecture was hugely appealing.
The potential beauty of gabion construction, both actual and latent, lies in its inevitable transformation over time by nature. Obviously gabion construction also lends itself to accelerated planting. The project was completed in early 1993.
In 1993, we approached the question of scale and vandalism for the design of the London Regatta Centre on the north side of the Royal Albert Dock. Initial investigations into the fill material included using the existing rubble and concrete left on the site and the use of waste glass – there were waste glass mountains in Europe at the time, and the cost was very low /m3. This offered the possibility of a light-transmitting wall. However, our tests showed that light would not enter through the probable thickness of the walls, and this coupled with the potential hazard risk of broken glass edges, led to a stone fill.
Funding was made available in 1996 for the 1st phase of the project, the boat house, for which we designed a modified gabion construction, consisting of a galvanized lightweight steel frame and weldmesh infill panel. This enabled a vertical curved rhythm to be developed for these long walls, giving both gravitas and a strong architecture to what could have been a vulnerable lightweight building in a relatively empty landscape.
ROYAL OPERA HOUSE, TOWER BRIDGE
In 1995, with Arup, Ian Ritchie Architects reinvestigated the way in which gabion could be fabricated and constructed with a view to improving and adapting their visual performance and the height of construction for the proposed Royal Opera House at Tower Bridge. The design exploited stainless steel for the baskets, horizontal retention cables, and river pebble fill.
The wall also addressed moisture penetration and acoustic issues.
