Geocomposites
A generic description for products made from any combination of two or more geosynthetic components to fulfill a specific function or functions. Examples being for drainage applications or separation and reinforcement functions.
Geosynthetic components can be combined together into a single geocomposite, thus providing savings in construction time and enhanced performance. Depending on the composite design, they can work as a barrier, drainage, filtration, protection, separation or reinforcement layer.
Geocomposites might be used as barriers/separation layers to separate and contain polluted soil (brownfield regeneration) or waste (landfill applications) and avoid migration of pollutants to the surrounding soil or water.
Geocomposites usually include a drainage layer to enable collection of seepage and/or gas and an impervious layer, such as a membrane. They can be mounted on solid frames to build below ground physical barriers, e.g. separation walls.
In railways applications, geocomposites can replace the sand layer separating the track ballast from the foundation, performing the same function of stopping the upward migration of fines.
Drainage geocomposites include geonets , but many other forms are available, e.g. band drains mounted on a geotextile or geomembrane (e.g. for landfill lining) or geocuspates, which are formed from sheets of polymeric material with an alternate stud and canal profile, bonded to geofabric filters, used for example in trenches alongside highways, behind retaining walls and bridge abutments, under embankments built over compressible soils, etc.
Drainage geocomposites that include geofabrics are used for filtration applications when there is a need to drain water out of the soil or for water to flow with soil fines being retained without clogging. Reinforcing geogrids can be added for applications where foundations or soil require strengthening.
Protection applications, alongside barrier applications, include sealing of buildings from hazardous ground gases, including methane and radon. Specific impervious layers are mounted on drainage geocomponents to stop the gases reaching the structure and to provide a collection route.
Geocomposites come to the fore in complex applications, such as in the protection of a river from potential leachate pollution from an adjoining Deep Morr Landfill. A geocomposite membrane with geotextile bonded to both sides was mounted on a curtain wall system and then buried as vertical barrier between the landfill and the river .
For the construction of a hardstanding area at the Edmonton waste to energy plant, North London, incinerator ash was chosen as fill. Protection to the membrane separating the ash from the foundation layers and collection of leachate percolating from the ash were required, hence a geocomposite was installed comprising a permeable, protecting geofabric bound to band drains connected to a collection sump.
- BS EN 14475:2006 Execution of special geotechnical works – reinforced fill
- BS EN 15237: 2007 Execution of special geotechnical works - vertical drainage
- BS EN 15382:2008 - Geosynthetic barriers. Characteristics required for use in transportation infrastructure
- BS EN ISO 11058:2010 Geotextiles and geotextile-related products. Determination of water permeability characteristics normal to the plane, without load
- BS 6031:2009 Code of practice for earthworks
- BS 8006-1: 2010 Code of practice for strengthened/reinforced soils and other fills
- Design Manual for Roads and Bridges, Volume 2 Section 1 Part 5, “BD 70/03 Strengthened/Reinforced Soils and Other Fills for Retaining Walls and Bridge Abutments. Use of BS 8006: 1995, Incorporating Amendment No 1 (Issue 2 March 1999)”, May 2003 .
- CIRIA Publication C516 Modular gravity retaining walls - design guidance, London 2000
- CIRIA Publication C573 Guide to ground treatment, London 2002
- CIRIA Publication SP123 Soil Reinforcement with Geosynthetics
- TRL Contractor Report CR341 Highway embankment over soft compressible alluvial deposits: guidelines for design and construction, Crowthorne, 1994
- TRL Project Report PPR341 Drainage of earthwork slopes, Crowthorne 2008
- CIRIA Publication SP123 Soil Reinforcement with Geosynthetics
- Geofabrics, geocomponents description
