Types of geotextile? Raw material & basic properties of geotextile?

As we know, the prefix of geotextile, geo, means earth and the ‘textile’ means fabric. Therefore, according to the definition of ASTM 4439, the geotextile is defined as follows

"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."

The ASAE (Society for Engineering in Agricultural, Food, and Biological Systems) defines a geotextile as a "fabric or synthetic material placed between the soil and a pipe, gabion, or retaining wall: to enhance water movement and retard soil movement, and as a blanket to add reinforcement
and separation." A geotextile should consist of a stable network that retains its relative structure during handling, placement, and long-term service. Other terms that are used by the industry for similar materials and applications are geotextile cloth, agricultural fabric, and geosynthetic.

THE TYPES OF GEOTEXTILE

In general, the vast majority of geotextiles are made from polypropylene or polyester formed into fabrics as follows:

• 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 MATERIAL 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

The oldest of these is polyethylene, which was discovered in 1931 in the research laboratories of the ICI. Another group of polymers with a long production history is the polyamide family, the first of which was discovered in 1935.The next oldest of the four main polymer families relevant to geotextile manufacture is polyester which was first announced in 1941.The most recent polymer family relevant to geotextiles to be developed was polypropylene, which was discovered in 1954. The comparative properties of these four polymer are shown in very general items in Table,

Here , 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

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