Using Nonwoven Geosynthetics
Nonwoven geotextiles are construction materials that should be used for separation/stabilization of materials in a non-dynamic area, filtration of water or gas, and for drainage. Unlike their woven counterparts, nonwoven fabrics aren’t designed to withstand heavy loading that could cause ripping. They are good for post-construction reinforcement and stabilization, and they are a better choice for special uses like the protection of geomembrane lining systems against exterior or interior penetrations.
When the soil conditions are good, contractors can place these products on paving or slabs to separate rock subbase from the underlaying compacted soil. The fabric layer keeps the rock from being pushed into the soil during concrete placement.
On pavements and streets, nonwoven geotextiles help avoid frost heave or subsidence at joints. The openings in the fabric mesh can be sized to allow water to pass through them. These features can prevent wash from the pavement’s base, and they can help direct water to the proper drainage spot.
Draining Wet AreasAnother common jobsite use of nonwoven geotextiles is to help drain wet areas. Since nonwoven geotextiles break down much faster than woven geotextiles their applications need to be static. Nonwoven geotextiles drain better than woven geotextiles where pooling or standing water is a problem.
Manufacturing NonWoven GeosyntheticsNonwoven geotextiles are manufactured much differently than woven geotextiles. Manufacturers produce nonwoven geotextiles by bonding their fibers and materials together, instead of weaving. This bonding action is accomplished using chemicals, heat, or needlepunching.
This process allows manufacturers to create nonwoven fabrics from a wide range of synthetic materials. You’ll notice that nonwoven geotextiles are felt-like in texture and appearance. Yet the process results in a very durable material when used in the right application.
Another attribute from the manufacturing process is that generally non-oven geotextiles have much higher elongation than their woven counterparts. A nonwoven geotextile specification often states that the fabric will elongate up to 50% more when compared to a woven alternative.
Contractors welcome this feature. First, the fabric’s stretching helps reduce any chance of aggregate puncture when placing coarse pieces of rock on the subgrade. The same elongation feature helps during installation. On many projects such as landfill covers or liner installation, the grade may be irregular due to the coarse rip rap layer, so the elongation helps with placement.
Manufacturers offer a wide array of nonwoven geotextile products. Contractors should note the weight of nonwoven geotextile products as the system differs from markups for woven materials. Nonwoven fabrics are described by ounces per square yard, typically in ranges of 4oz, 6oz, 8oz, 10oz, and so on. The higher the weight the more heavy-duty the fabric.
Weight ranges for nonwovens fall into 3 general application categories:
- Nonwoven geotextiles in their lightest weight are used for soil separation and drainage in light duty landscape applications. This geotextile is designed to withstand many environmental problems found in parks, golf courses, and sports park construction projects.
3. For projects that require long-term durability along with high puncture resistance, transmissivity and permittivity, heavy weight nonwoven geotextiles are preferred.