Using Geotextiles in Drainage Systems

How do you create a robust drainage system capable of collecting liquid waste in containment systems while providing filtration? Geotextile membrane solutions represent the modern tool used in primary and secondary leachate collection systems beneath solid waste and as a cover for surface water and gas removal systems. Geotextiles outperform rock and soil because they are human-made solutions that offer reliable, predictable performance and install in less time compared with traditional drainage options.

We will explore the use of geotextile membrane in applications that require drainage piping and leachate collection systems commonly found in environmental applications such as landfills and mines.

Geotextiles in action

Geotextiles are also referred to as filter fabrics or construction fabrics and consist of polymeric yarns and/or fibers made into woven or nonwoven textiles supplied to job sites in large rolls. Nonwoven needle-punched geotextiles are manufactured by passing a fiber web through a needling process wherein barbed needles penetrate the web and entangle numerous fibers transverse to the plane of the web to form a fabric. Once fibers are in a fabric form, they pass over a heated roller resulting in a singed or burnished surface of the fibers on one or both sides of the fabric (1). Finally, the fabric is wound up into large rolls and a protective covering is applied for storage and shipping.

When ready for placement at the job site, the rolls are removed from their protective covering, properly positioned, and unrolled over the substrate material. The substrate is usually a geonet, geocomposite, drainage soil, or other soil material. The roll edges and ends are either overlapped for a specified distance, or are sewn together.

Upon receiving quality assurance approval, the geotextile can then be covered with an overlying material. The choice of material will depend on site-specific conditions and can be geomembrane, geosynthetic clay liner, compacted clay liner, geonet, or drainage soil.

Using geotextiles to create a drainage system

In most filtration applications, geotextiles are implemented in conjunction with systems where water flow is either horizontal or has a downward component. There are, however, applications where the hydraulic gradient has an upward movement, which induces piping of the soil. In this situation, geotextiles are used as a filter between silty sand and the stone bedding around the pipes. In this usage, the pipe is installed to help lower the water table, promoting an inward and upward gradient. The geotextile’s role is crucial, as it allows the movement of water into the hydraulic control layer while preventing the significant movement of soil.

Designing the right geotextile to perform this role requires several considerations. First, you must choose the correct design for the application as well as the suitable filter. Second, you must choose a geotextile with filtration properties that align with the soil type at the location to account for variability. Finally, you have to implement sufficient quality control schemes and ensure there are adequate construction specifications (2).

Using AGRUTEX in your next drainage system

AGRU America produces a polypropylene-based nonwoven geotextile that offers superior drainage properties in a high-quality manufactured product that offers long service life thanks to its robust high strength as well as high chemical and ultraviolet resistances. In most environmental construction projects, geotextiles must not only provide reliable filtration, but also possess high strength to withstand the installation process—especially in constructions where the geotextile will be in contact with coarse stone.