Pavingexpert.com WWW
	Geo-fabrics

Introduction   Types   Uses   Specification   Links

Landscape Fabrics   Geo-fabrics   FAQ - is a membrane necessary   Sub-grades   Sub-bases   Aggregates

Introduction Reading the trade press, it would seem that civil engineers are finding a new use for Geo-fabrics on an almost daily basis. Although the term 'geo-fabrics' is used here, this group of ground engineering products includes geo-synthetics, geo-membranes, geo-textiles, landscape fabrics, geo-grids, and geo-matrices. Basically, they are all sheet products of synthetic or natural origin that are used in some way to 'improve' the natural ground or earthworks.   Some definitions Geo-synthetics is a 'catch-all' term used to describe sheets of a man-made material that may be knitted, woven or non-woven.
		Geo-textiles are woven, non-woven or knitted, permeable sheets, usually, but not exclusively, non-biodegradable. Landscape fabrics are an example of a light-use geo-textile commonly used in the horticultural and soft-landscaping trades.
		Geo-membranes are impermeable and usually non-woven, ie a film or solid sheet. Typical use would be as a vapour or damp barrier.
		Geo-composites normally refers to a sheet that combines two or more layers of geo-synthetics. For example, a drainage composite usually combines a permeable geo-textile with an impermeable geo-membrane.
		Geo-grids are tough, non-woven synthetic sheets with large (100mm+) rectanglar holes. Used for ground stabilisation. They are also known as geo-nets.
		Geo-matrices can be thought of as 3-dimensional geo-grids, in that they are cellular and used to stabilise surface soil, gravels etc. More commonly used as a form of Grass Paving - See also Cellular Paving Systems page.
Many types of materials may be used to manufacture geo-fabrics, depending on the end use. The two main distinctions are between woven and nonwoven products. Most geo-fabrics are manufactured from synthetic materials, but there are some applications that call for biodegradable, natural materials such as coir or jute. Polypropylene is a popular choice for geo-grids or geo-matrices, as it is strong and chemically inert. Polyester is chosen for its strength and flexibility. There are permeable woven geo-textiles commonly used for filtration purposes and impermeable membranes to resist mud-pumping. Some fabrics offer high puncture resistance, an important consideration in raod and rail construction projects, or where the integrity of the sheet is essential, as in landfill sites.

Uses Geo-fabrics have three main roles in the construction industry. They are used to provide... Separation Filtration (liquids and gases) Reinforcement ...either singly or in combination. Geo-fabrics have literally hundreds of uses, but the most common include...
Roads & Pavements		Maintaining sub-base integrity
Separation:	-to prevent bedding layers disappearing into sub-bases/subgrades -to keep sub-bases from mixing into sub-grades -to minimise/prevent soil-pumping
Filtration: Reinforcement:	-as drainage composites or lagging to filter drains -to inhibit reflective cracking in asphalt courses -strengthening of poor sub-grades
Railway Construction
Separation:	-similar uses to those in road construction -separation of ballast from sub-grade to minimise 'pumping'
Filtration: Reinforcement:	- track-edge drainage -sub-grade and sub-base reinforcement
Ground Engineering
Separation:	- weed control; root barriers	Root Barriers protect drainage and foundations
Filtration:	- usually as a drainage composite but also as a filter membrane for land drains
Reinforcement:	- used to stabilise topsoils - to stabilise earth banks

Other Uses
Erosion Control:	- to prevent coastal or fluvial erosion - to counter scour by wind and rain and surface run-off - may be biodegradable and intended to last only until vegetation has established itself
Vapour/Gas membranes:	- impermeable to protect part of a structure - damp-proofing; radon barriers
Landfill Sites:	- containment and filtration - leachate and gas collection

"Do I really need a membrane or a layer of polythene underneath my paving?"           [Click Here]

Specification Separator geo-fabrics are the most commonly used geo-synthetics used in the construction of roads and pavements. These are often non-woven, permeable materials primarily used to prevent the various layers of a pavement mixing or disappearing into lower layers. DTp Clause 609 lists 4 essential qualities for separator geo-textiles: Pore size O90 - a measure of average hole size - lower figure means finer particles trapped Permeability, as measure in litres per m² per second Tensile strength - usually an abitrary minimum of 10 kN per m² Puncture resistance (CBR)

Links: Hy-tex - Textiles for Civil Engineering, Construction, Landscaping, Horticulture and Agriculture Terram Trade - Geo-synthetics and Drainage Composites TDP Limited - TDP115 geo-membrane Peter Scott Tree Care - Root barriers Polyfelt - Geosynthetics for the Civils and Construction Industry Geo-Fabrics - Non-woven geosynthetics

Related Pages Sub-grades Sub-bases Geo-fabrics Landscape Fabrics Aggregates