Geotextile is a synthetic permeable material used to improve the soil characteristics in civil construction projects. Geotextiles are large sheets that bind the earth’s soil strongly and prevent it from damage during rainy days and make poor soil more suitable for construction projects. Geotextiles are ideal for construction and infrastructure work like roads, harbors, buildings, landfills, dams and many other civil engineering projects.
Geotextiles also have the ability to filter, reinforce, separate, seal and protect. It also improves soil characteristics like friction restraint, support of loads and prevents soil erosion while allowing water to drain off.
To further understand the importance and role of geotextiles in construction, lets dive into the types and functions of geotextiles.
Types of Geotextiles
Geotextiles are made from polyester, polypropylene, polyethylene, nylon, fiberglass and polyvinylidene chloride. In most civil construction projects, polyester and polypropylene based geotextiles are commonly used. According to the manufacturing process, they are divided into 3 main categories.
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Woven Fabric – These are the most commonly found geotextiles and the manufacturing techniques are similar to the usual clothing textiles. They have the characteristic appearance of 2 sets of parallel threads or yarns. Along the length yarn is called warp and the one perpendicular is called weft. Nonwoven Fabric – These are made from either continuous filament yarn or short staple fibers. The fibers are bonded using thermal, chemical or mechanical techniques, or a combination of them. A process of endless filaments is used in the manufacturing techniques to ensure the use of high-quality materials. Knitted – These are manufactured by interlocking a series of loops or yarn together. All the knitted geosynthetics are made using knitting techniques with other methods like weaving.
Functions of Geotextiles
As mentioned earlier, geotextiles are used to improve the soil characteristics before building embankments, pipelines, roads and earth-retaining structures. Let’s take a look at the main functions of geotextiles.
Separation
This is the main reason why geotextiles are used in civil construction projects. To prevent intermixing of two different soil when water gets into soil strata, geotextile is installed between them. This ensures that the soil characteristics are conserved. In the case of roads, separating the fine subgrade soil from the aggregates preserves the strength of base materials and drainage properties.
One of the main functions of geotextiles is to prevent soil contamination and enable water flow without compromising the structural integrity. Some application areas are:
Between landfills and stone base courses Between subgrade and base in paved and unpaved roads Between railroads subgrade Between geomembrane and sand drainage layers
Filtration
Filtration property is useful when there is a need for water to move in both directions in the drainage system. Filtration geotextiles can be woven or non-woven, and are used to prevent movement of fine aggregates between the soil layers.
The 2 main properties involving filtration are porosity and permeability. Based on these properties, geotextiles can promote lateral flow of water for dissipating kinetic energy from capillary groundwater rise. Filtration applications can be both horizontal and vertical for solving drainage problems along roads and other structures.
Reinforcement
The role of reinforcement is similar to the role of steels bars in concrete construction. By implementing the design parameter provided by the geotechnical engineers, geotextiles are used for embankments and roads that are built on poorly graded soils.
The soil strength in introduced in the following 3 mechanisms:
Friction and movement restraint between geotextile and soil Membrane type of support for any loads present Forcing the surface failure plane to develop higher shear strength surface
Sealing
Geotextile fabrics can be filled with asphalt, which makes them impermeable and capable of stopping the vertical flow of water. For this, non-woven geotextiles are preferred. Impermeability can prevent the contamination of soil or groundwater from the pollutant above. This in turn, will help in preventing the loss of water due to evaporation.
Applications of Geotextiles in Civil Engineering
The scope of geotextiles in civil engineering is very vast. Below are some of the more common applications of Geotextiles:
Roads – Used for reinforcing the additional tensile strength of soil for road construction. Also, can be used for rapid dewatering in the roadbed.
Railways – Used for separating the individual soil layers without hampering the groundwater circulation where the ground is unstable. This is useful to keep the ground layers stable during constant shocks and vibrations from a passing train.
Agriculture – Used for mud control to improve cattle paths by using non-woven fabrics.
Coastal Work – Used for preventing erosion in river banks, canals and other water bodies.
Some other applications are landfills, sidewalks, parking lots, green areas, duct banks, recreational facilities, etc. Geotextiles also have a positive environmental impact.