What Is the Difference Between Non-woven Geotextile and Woven Geotextile on Filtration and Drainage?

It is well known that in the field of geosynthetics, almost all engineering projects rely on geotextiles. As a type of geosynthetic material, geotextiles have multiple functions such as filtration, drainage and protection. Among these, filtration and drainage are extremely important, which are related to the long-term stability of impermeable drainage projects. Therefore, this article will mainly introduce the differences between the two in terms of structure and application.

First, they have difference processes:

Non-Woven Geotextile:

The production is not traditional spinning and weaving steps. Filament or staple fiber geotextiles are formed by laying fibers on machine to create a loose web. And then it will be consolidated through needle-punching, heat-bonding or chemical bonding, which entangle and bond the fibers together. The final product is a three-dimensional, isotropic entangled fiber structure (similar to felt) with a random pore size distribution.

Woven Geotextile:

Polypropylene or polyester tapes are typically used as warp and weft yarns. These are interlaced in a regular pattern on a loom in plain or twill weave. The final product is a two-dimensional, regular and planar mesh structure. The shape and size of its pores are related to the spacing and thickness of the yarns.

Besides, the different manufacturing processes lead to differences in filtration and drainage performance:

Non-woven geotextiles generally offer superior drainage and filtration compared to woven geotextiles. The reasons are as follows:

1. Non-woven geotextiles provide better water passage paths: When liquid flows within the plane of a non-woven fabric, the random fiber structure creates internal pathways that are three-dimensional and tortuous, allowing water to pass through more readily. The woven process inherently results in fewer inter-layer spaces, making the fabric more reliant on pores perpendicular to its plane for drainage. Structurally, this means the in-plane water transmissivity (or hydraulic conductivity) of non-woven geotextiles is typically higher than that of woven ones.
2. Non-woven geotextiles provide a better filtration barrier: The internal structure of non-woven geotexitle consists of randomly oriented fibers. They can create pores of varying sizes, allowing them to block particles in different dimensions. Furthermore, when they contact with soil, some of the finest particles may be carried by water flow and retained within or on the surface of the fabric. This process is known as the "bridging effect," , which can form a denser filter layer composed of the soil particles themselves, thereby enhancing filtration performance. In contrast, the filtration efficiency of woven geotextiles depends on the uniformity of pore openings. Under dynamic loading or high hydraulic gradients, the locking effect of regular pores is weaker than the entanglement structure. Additionally, the relatively rigid woven surface conforms less effectively to soil, so it is difficult to adapt to settlement and deformation.

Based on the above, we can define different application scenarios for the two types of geotextiles:

Non-Woven Geotextile for:

• Drainage wrap and filtration: Wrapping around French drains, drainage pipes, or sand drains.
• Geomembrane (e.g., HDPE) protection layer: Placed above and below geomembranes to protect the geomembrane from sharp objects while providing a drainage interface.
• Erosion control and filtration on slopes, riverbanks and coastlines: Placed between soil and riprap (or concrete blocks) to prevent soil loss.
• Combined with vertical drains: Often used with prefabricated vertical drains (PVDs) as a filter layer.

Woven Geotextile for:

• Reinforced soil structures: Used in reinforced retaining walls, steep slopes, and for subgrade reinforcement, where high tensile strength and low elongation are key.
• High stiffness and clear separation: Placed between soft subgrades and fill to separate different soil layers, prevent mixing and contribute to load distribution, leveraging its high strength and low extensibility.
• Precise filtration: When specific particle sizes must be strictly controlled from passing through, its regular pore openings provide more predictable performance.

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