Geotextiles is defined as permeable textile materials used in contact with the soil, rock, earth etc as an integral part of civil engineering project, structure, or system. Different type of Geotextiles are Filtration, Drainage, Separation, Reinforcement and Sealing.
Separation - The introduction of a flexible porous textile placed between dissimilar materials so that the integrity and functioning of both the materials can remain intact or be improved.
Filtration - The equilibrium geotextile to soil system that allows for adequate liquid flow with limited soil loss across the plane of geotextile over a service lifetime.
Drainage - Ability of thick nonwoven geotextile whose 3-dimensional structure provides an avenue for flow of water through the plane of the geotextile.
Reinforcement - Improvement in the total system strength created by the introduction of geotextile into soil.
Sealing - The classic application of a geoxtile as a liquid barrier is paved road rehabilitation. It minimizes vertical flow of water into the pavement structure
Types of Geotextiles
1) Woven fabrics
2) Non-woven fabrics
3) Knitted fabrics
Different design properties are
1) Puncture Strength - To measure puncture resistance. Stimulates puncture strength to static load of aggregates. Resistance to puncture measured in Newton.
2) Burst Strength - Stimulates strength of geotextile to a continuous hydraulic load. Force causing rupture recorded in units of pounds per square inch or Kilo Pascal.
3) Dynamic Puncture - To measure the strength of geotextile to falling objects. Stimulates placement of aggregate over geotextile during installation stage expressed in mm.
4) Permeability - Measures the rate at which liquids can pass through the geotextile. Expressed in liters per square meters per second.
5) Apparent Opening Size (AOS) - Reflects approximate largest opening dimension available through which the soil may pass. Expressed in mm.
6) Grab Tensile Strength and Elongation - Measures tensile strength and elongation along the plane of the geotextile by loading it continually. Value of breaking load expressed in Newton and elongation at break in percent.
Different areas of application are Flexible paved road construction, Drainage applications and Pavement overlays.
Benefits of using Fabric Interlayer are waterproofing of the lower layers. Retarding reflection cracking in the overlay. Increase in structural stability. Absorption of stresses. Reduces permeability of a pavement. Reduces infiltration of moisture. Maintains the strength of subgrade, sub base and base course. Limiting damage due to saturated condition pore pressures.
Geotextiles are an efficient effective and economic method of solving most of the geotechnical problems in roads. The design engineer should be well aware of the possible problems and should use this relatively new tool for solving them. For this he/she should understand properties and capabilities of the geotextile material.