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What is geotextile

Views: 222 Author: bingo Publish Time: 2016-03-28 Origin: Site

What is geotextile?

geo means earth and the textile means fabric. According to the definition of ASTM 4439, it defines "A permeable geosynthetic comprised solely of textiles. Geotextiles are used with foundation, soil, rock, earth, or any other geotechnical engineering-related material as an integral part of human-made project, structure, or system."

Types of geotextile

Generally speacking, main kinds of geotextiles using polypropylene or polyester are formed into fabrics by following ways:
· Woven monofilament
· Woven multifilament
· Woven slit-film monofilament
· Woven slit-film multifilament
· Nonwoven continuous filament heat bonded
· Nonwoven continuous filament needle-punched
· Nonwoven staple needle-punched
· Nonwoven resin bonded
· Other woven and nonwoven combinations
· Knitted

Raw materials of geotextile

The four main polymer families most widely used as the raw material for geotextiles are:
1. Polyester
2. Polyamide
3. Polypropylene
4. Polyethylene

Difference of these items are as follows:

	Polyester	Polyamide	Polypropylene	Polyethylene
Strength	H	M	L	L
Elastic modulus	H	M	L	L
Strain at failure	M	M	H	H
Creep	L	M	H	H
Unit weight	H	M	L	L
Cost	H	M	L	L
Resistance to:
U.V. light stabilized	H	M	H	H
unstabilized	H	M	M	L
Alkalis	L	H	H	H
Fungus, vermin	M	M	M	H
Fuel	M	M	L	L
Detergents	H	H	H	H

H: High; M: Medium; L: Low

The basic properties of geotextile

The properties of polymer material are affected by its average molecular weight (MW ) and its statistical distribution. Increasing the average MW results in increasing:
· tensile strength
· elongation
· impact strength
· stress crack resistance
· heat resistance

Narrowing the molecular weight distribution results in:
· increased impact strength
· decreased stress crack resistance
· decreased processability

Increasing crystallinity results in:

· increasing stiffness or hardness
· increasing heat resistance
· increasing tensile strength
· increasing modulus
· increasing chemical resistance
· decreasing diffusive permeability
· decreasing elongation or strain at failure
· decreasing flexibility
· decreasing impact strength
· decreasing stress crack resistance

The basic function of geotextile

There are at least 80 specific applications area for geotextiles that have been developed; however, the fabric always performs at least one of five discrete functions:

1.Separation

Geotextiles function to prevent mutual mixing between 2 layers of soil having different particle sizes or different properties.

2.Drainage

The function of drainage is to gather water, which is not required functionally by the structure, such as rainwater or surplus water in the soil, and discharge it

3.Filtration :

Filtration involves the establishment of a stable interface between the drain and the surrounding soil. In all soils water flow will induce the movement of fine particles. Initially a portion of this fraction will be halted at the filter interface; some will be halted within the filter itself while the rest will pass into the drain. The geotextile provides an ideal interface for the creation of a reverse filter in the soil adjacent to the geotextile. The complex needle-punched structure of the geotextile provides for the retention of fine particles without reducing the permeability requirement of the drain.

4.Reinforcement

Due to their high soil fabric friction coefficient and high tensile strength, heavy grades of geotextiles are used to reinforce earth structures allowing the use of local fill material.

5.Protection:

Erosion of earth embankments by wave action, currents and repeated drawdown is a constant problem requiring the use of non-erodable protection in the form of rock beaching or mattress structures. Beneath these is placed a layer of geotextile to prevent leaching of fine material. The geotextile is easily placed, even under water.