Geocells
A deep (1m) layer of interconnecting strips of geogrids/geofabrics filled with granular material to create a stiffened basal layer which can be used to control differential settlement under embankments constructed on compressible ground.
Geocells provide three dimensional reinforcement to soil by physical confinement into a honeycomb like structure.
Geocells might be made of polymeric fabric or grids and are delivered to site flat-packed, ready to be opened up and positioned, possibly with the aid of struts to keep the cells open and in certain cases a frame to pretension the structure, and then filled.
Usually, soil, sand and fine granular fill (i.e. compactable materials) are used; coarser granular materials are not as suitable as they would not pack enough and potentially tear and damage the cells. In some applications, concrete might be used as infill.
Geocells can be used as basal reinforcement to embankments or as sub-base reinforcement to paved and unpaved roads. Because of their geometry, they act to distribute vertical load and behave as a semi-rigid slab so limiting embankment and/or road settlement. They can be used over soft compressible soils or to limit the thickness of the subbase layer required.
Geocells have been used for reinforcing road verges and improve their drainage. They do not require a specific foundation as, due to the honeycomb structure, potential traffic (vertical) loads are more evenly distributed within the geosystem. Excavated soil, provided it is not too coarse, can be used as backfill.
Geocells are permeable to water when filled with loose soil or granular material. This characteristic enables them to be used for erosion protection of banks and beds of rivers, canals and lakes.
They can also support vegetation, and can be installed on gentle slopes where they provide a restraint to downward migration of the soil.
Because they can be transported and handled easily, installed rapidly, and filled with locally available materials, they have found applications as building elements for earth retaining structures, noise bunds, semi-temporary walls, stand-alone barriers and bunkers, for military defence systems.
The filled honeycomb mattresses can be stacked almost vertically and offer good acoustic, blast and ballistic protection thanks to the dampening properties of their composite structure. Furthermore, failure of a single cell does not in general compromise the rest of the honeycomb structure and local repairs can be carried out easily.
Geocells provide strong foundation mattresses for a diverted road to be built over uncompressed fill in old open mining voids at the Steadsburn Surface Coal Site at Widdrington, Northumberland. The geocell solution was adopted as an alternative to more costly reinforced concrete slabs and piling .
Geocells were used to build an environmental bund at a natural turf sport pitch in Sheffield. The locally available soil of very low shear strength could then be used, saving the costs of buying and importing better quality granular fill. The bund was profiled to the required shape and geocells were installed on the slope surface to retain the topsoil, reduce erosion and promote vegetation growth .
- BS EN 14475:2006 Execution of special geotechnical works – reinforced fill
- BS 6031:2009 Code of practice for earthworks
- BS EN 1997-1: 2004 Eurocode 7: geotechnical design
- BS 8002:1994 - Code of practice for earth retaining structures
- BS EN 13253:2001 - Geotextiles and geotextile-related products. Characteristics required for use in erosion control works (coastal protection, bank revetments)
- BS EN 15381:2008 - Geotextiles and geotextile-related products. Characteristics required for use in pavements and asphalt overlays
- BS EN ISO 13426-1:2003 - Geotextiles and geotextile-related products. Strength of internal structural junctions. Geocells
- BS EN 13249:2001 - Geotextiles and geotextile-related products. Characteristics required for use in the construction of roads and other trafficked areas (excluding railways and asphalt inclusion)
- BS EN 13251:2001 - Geotextiles and geotextile-related products. Characteristics required for use in earthworks, foundations and retaining structures
