Difference between non-woven and woven geotextiles
Geotextiles are geosynthetic materials with several applications in civil engineering. These robust synthetic fabrics are manufactured for multiple uses like soil stabilization, erosion control, construction, drainage and many such geotechnical projects. They are generally prepared from either polypropylene or polyester, as these are highly resistant to rot and corrosion. The most common types of geotextiles are woven and non-woven fabric. Before explaining how a non-woven geotextile differs from a woven geotextile material, let’s first understand the features and benefits of each type.
What is a woven geotextile?
Woven geotextiles are produced when single yarns are woven together in a loom. The base material from slit films, fibrillated yarn to monofilaments, but the weaving process remains the same. This yields tough and durable geo-fabrics that are used for roadways, driveways, residential streets, and highway applications.
Although it’s less porous than other geotextiles, woven geotextiles serve long-term separation and reinforcement needs. Its corrosion resistance ensures durability in even adverse chemical environments.
What are the functions of woven geotextiles?
- Reinforcement: Woven geotextiles are designed to reinforce structures by being installed between soil layers. This configuration helps prevent shifting and mixing of these layers, contributing to overall stability.
- Separation: Another critical, and well-loved, feature of woven geotextiles is material separation. For instance, a woven geotextile can be used in a landfill to separate the waste from the soil underneath.
- High load-bearing capacity: Woven geotextiles are manufactured to resist loads, making them suitable for applications where the subgrade is under heavy and continuous pressure or weight. Road construction is a fine example; it needs a geotextile strong enough to bear the heavy load and weight caused by traffic.
- Impermeability: Woven geotextiles are relatively impermeable, making them a good choice for projects that require strength, stability, and resistance to corrosion. These geotextiles are not ideal for drainage projects.
- Tensile strength: Tensile strength refers to the maximum tensile force that a geotextile can withstand without breaking. This property is crucial as it directly impacts the performance of the material in various applications. A geotextile with high tensile strength is essential for effectively supporting mechanical loads, ensuring stability and durability in construction projects. Understanding the tensile strength of a geotextile helps in selecting the appropriate material for specific engineering needs.
Applications of woven geotextiles
Woven geotextiles are a material of choice for its five inherent material properties which are mechanical, chemical and physical in nature. These material features make geotextiles a preferred choice to use in a number of industries –where construction needs to be optimized. One of the reasons this geosynthetic product has gained favour is that it solves many geotechnical challenges, while providing longevity and resistance to physical elements.
- Highways: Chosen for their ability to reinforce the base of the paved road or highway, geotextiles reinforce the road base and prevent it from shifting apart or sinking under heavy traffic loads. Separating the road base from the subgrade improves the integrity and longevity of the road. Geotextiles prevent the erosion of road slopes and embankments. They are preferred for drainage situations within the road base so that water doesn’t accumulate, causing deformation, pore pressure, and rutting. When applied to the base, it helps to filter out soil migration from the sub-grade which typically leads to settlement and deformation issues over a period of time.
- Residential streets: Although similar to highways, woven geotextiles are used for residential street construction. Woven geotextiles reinforce the base of the road to prevent it from yielding or stripping, and the spacing between the bases prevents potholes. Slopes and embankments in residential areas are kept from eroding through woven geotextiles.
- Parking lots: These areas typically see repetitive loading of the same type, apart from experiencing more temperature extremities. From a design standpoint therefore, woven geotextiles are used for reflective cracking and to reduce the development of pits and potholes caused by heavy vehicle traffic. We also need to account for thermal expansion, and contraction. Woven geotextiles improve parking lot pavement performance, and can help with settlement reduction by about 30%. Here, they reinforce the pavement against excess cracking from vehicles with heavier traffic. They reduce pavement interaction to subgrade, thus enhancing durability within the parking lot; in general delivering an improved lifespan by 5-7 years.
- Basal reinforcement for embankment over soft soil: Woven geotextiles improve the distribution of loads applied to the embankment structure reducing the excessive settlement or failure of the soft soils. This creates an even distribution of loads over a larger area, thus preventing the local stress concentrations that otherwise lead to deformation. By providing tensile strength, the woven geotextiles enhance the shear resistance by acting as a reinforcement layer and prevent sliding or slumping.
- Load transfer platforms (LTP): Woven geotextiles are commonly used in design and construction of load transfer platforms. When installed in LTP, woven geotextiles provide lateral and vertical reinforcement, thereby limiting soil movement. It also creates a stiffening effect that resists the compression of the granular layers above it. Furthermore, the separation function prevents the degradation of the granular fill, preventing soil clogging and internal erosion.
- Under driveways: Woven geotextiles create an essential underlayment for driveways, reinforcing durability and functionality. They reinforce the base course of the driveway to prevent road sinking and ugly rut formation. Woven geotextiles drastically improve the overall performance of driveways by immediately rack support over the subgrade. They also help reduce erosion where the driveway slopes upwards or downwards.
What is a non-woven geotextile?
Non-woven geotextiles are manufactured by needling the fibres, among other mechanical entangling forms. They are mainly made from synthetic polymers, including polyester and polypropylene, and their strength is improved mostly through heat treatment, making them highly permeable.
Non-woven geotextiles are commonly used in projects for protection, filtration, separation, and drainage. However, they are generally less strong than woven geotextiles.
What are the functions of the non-woven geotextiles?
- Filtration: Non-woven geotextiles perform well in filtration. They allow fluid to pass through a porous structure while retaining solids and contaminants, making them useful in water filtration, wastewater treatment, and soil erosion control.
- Segregation: Woven geotextiles serve as separators, but non-woven geotextiles are better for keeping materials apart. Nonwovens prevent the mix or combined actions of various materials. This ability is highly useful in applications like landfill liners, where the geotextile is going to be a barrier between the waste and the earth underneath.
- Drainage: The porosity of nonwoven geotextiles facilitates drainage. They are indispensable in providing better drainage to regions lacking good soil conditions and excessive moisture. Such materials are frequently used in landscaping, construction, and agriculture.
- Permeability: Outstanding permeability is among the critical effective properties in describing nonwoven geotextiles. This immediately conveys that fluid can pass directly through such fabric. Therefore, it is suitable for applications requiring filtration, drainage, and separation.
- Weight classification: Nonwoven geotextiles are generally classified by weight per unit area. The following is important to consider in selecting geotextiles for an application, as weight will affect a whole host of other things, including, but not limited to, strength and permeability for a given fabric.
Applications of non-woven geotextiles
- Under rock riprap revetments: Nonwoven geotextiles are also placed under rock riprap revetments, serving numerous advantages. They act as a filter to hold the soil in position and prevent it from clogging the voids between the rocks due to soil washing. This protects the revetment structure, keeping soil erosion beneath the revetment at bay.
- Enveloping french drains: Unbonded geotextiles are most commonly used to envelop French drains. This protects against the drain getting clogged by filtering soil particles, increases drainage for water flow with a smoother path for the movement of water, and prevents possible erosion around the drain.
- Alternative subsurface drainage solutions: Nonwoven geotextiles make sense as an option for replacing drainage networks, such as perforated pipes and wick drains, in a subsurface drainage system. This will prevent drainage systems from clogging, increase the flow of water through the systems, and aid in preventing erosion around them.
How is a non-woven geotextile different from a woven geotextile material?
- Application: Woven geotextiles are most often used for reinforcement and stabilisation purposes. Since they are very tough and have high strength, woven geotextiles are highly suitable for roadways. Filtration, separation, and drainage can advantageously make non-woven geotextiles their utility field; therefore, they are ideal for water filtration, wastewater treatment, and landfill liners.
- Manufacturing: A loom turns single yarns into woven fabric; hence, in these specific cases, the woven geotextiles have a higher structure and tensile strength. However, the normal ways of manufacturing nonwoven geotextiles by bonding short and long fibres rely on the working of certain needle-punchings or heat treatments to knit nonlinear structures into a relatively permeable, less-structured fabric.
- Properties: Geotextiles are all about high load capacity and tensile strength. Hence, they apply where strong and tough fabrics are necessary. On the other hand, non-woven geotextiles usually tend to be more porous than their woven counterparts, whereby fluid flows through them easily. These properties make them very suitable for use in filtration and drainage applications. More structured design of geotextiles woven through allows to have thence on average a lower flow-through rate, without doubt; nonwoven ones have an open structure and, therefore, manage a higher flow-through rate.
- Materials: Mainframe Woven or nonwoven geotextiles can be manufactured from polyester or polypropylene yarns and fibres; the type of material used depends on project requirements.
In summary, woven and non-woven geotextiles are uniquely designed with distinctive features that differentiate them based on their applicability. Woven geotextiles provide better reinforcement and stabilisation, while non-woven geotextiles are great for filtration, separation, and drainage.
The choice of geotextile will balance woven and non-woven, depending on the project requirements. In either case, specific load capacity, tensile strength, permeability, and flow-through rate information must be carefully studied.