Different production process of geotextiles | Applications

The production process of geotextiles

Most geotextiles are produced using classic or conventional fabric production techniques. Manufacturing processes for geotextile production can be broadly classified into three categories, (i) classic, (ii) specialized, and (iii) composite geotextiles. In classic geotextiles, textile industry products, such as woven, knitted, nonwoven fabrics, etc., are considered, whereas special geotextiles, despite having the appearance of classic geotextiles, are not direct products of textile technology, such as webbing, Matte, and mesh.

Classic geotextiles are made in two steps, such as making fiber, filament, slit film (tape), or yarn and then converting these elements into fabric. The ingredients needed to make geotextiles are made using a variety of techniques, which are discussed below.

Filaments

Filaments are produced by various extrusion techniques, such as wetting, drying, and melting. Molten extrusion is used for polymers such as polyester and polypropylene, which are widely used in the manufacture of synthetic fiber-based geotextiles. Here, molten polymers are extruded through spinnerets or dies and subsequently, they are drawn along the filament axis in such a way that molecular orientation along the filament is improved, resulting in high tensile properties. When numerous filaments are pulled out simultaneously by spinnerets, it is known as multifilament yarn.

Short (staple) fibers

The filaments are cut into short lengths of 2 to 10 cm, known as staple fibers. These staple fibers are twisted together to make yarn.

Slit films

The films are made by the process of molten extrusion using slit dice which are then cut with a sharp blade. These films can be further fibrillated and divided into fibrous strands, known as fibrillated yarn.

The constituent materials (filament, fiber, slit film, or yarn) are converted into a variety of classical and special geotextiles.

Classic geotextiles production process

Different types of classic geotextiles production processes, which are briefly discussed below-

Woven geotextiles

A woven fabric consists of two sets of orthogonal interlaced filaments or staple-fiber yarns. Weave design is the method by which yarns or filaments are joined together. Filaments or threads placed on the longitudinal and transverse sides are known as warp and weft, respectively. Monofilament and slit woven geotextiles are expected to be thinner than multifilament, spun, and fibrillated woven geotextiles.

Nonwoven geotextiles

Nonwoven fabrics are referred to as a sheet, web, or batt or are randomly bound by fiber/filament, friction, and/or solidification, and/or adhesion. In general, the formation of nonwoven fabric can be considered a two-step process: web formation and bonding of these fibers by mechanical, thermal, or chemical means. This two-step process has created a classification of non-woven structures, such as carded, air-laid, spunlaid, melt-blown, needle punched, hydroentangled, adhesive bonded, thermally bonded, stitch-bonded, and so on. Some important processes that are used to make nonwoven geotextiles are Spin laying, chemical bonding, mechanical bonding, and Thermal bonding.

Knitted geotextiles

These are produced by interlocking a series of filaments or threads to form a planar structure. The loops of the knitted structure are interlocking in different ways like the weave designs of the woven fabric.

Braided geotextiles

Braiding is usually used to make a thin rope-like material by interlacing three or more strands of filament or yarn diagonally. The topology of strand interlacement in a braided structure is similar to that of a woven structure. Therefore, the plain, 2/2 twill and 3/3 twill are similar to the diamond, regular and Hercules braid structures, respectively. Furthermore, braided structures can be classified as two-axis and three-axis braids; Both have two sets of braided strands, each strand aligned with the bias direction, but the latter also has an additional set of strands aligned parallel to the braid axis.

Special geotextiles production process

Webbings

These are produced from strips of medium width and resemble thick woven slit film fabrics.

Mats

These are made from thick and rigid filaments of solid shape like open non-woven fabrics.

Nets

These consist of two sets of extruded strands lined up in the bias direction and are usually partially melted into one or both strands. These net structures can also be produced using a molten extrusion process that consists of a rotating dye with a slot on the border through which the molten polymer is extracted.

Composite geotextiles production process

In addition, composite geotextiles can be made by combining several of the products listed above. For example, a combination of multiple layers of knitted / woven / non-woven material can be made by stitching, needle punching, thermal bonding, etc.

Applications of geotextiles

i. Retaining walls

ii. Steep slopes

iii. Landslide repairs

iv. Soft-soil embankments

v. Embankments on very soft soils, combined with vertical drains

vi. Roadway reinforcement

vii. Reinforcement under tramways or railway ballast

viii. Erosion control in sea embankments and waterworks slopes or beds

ix. Reinforcement of foundation layers

x. Reinforcement or bridging over potential weak zones, voids, or cavities Piled embankments with basal reinforcement.

xi. Sealing membranes.

xii. Hydraulic structures (dams, irrigation channels).

xiii. Sealing systems of buildings.

xiv. Buried piping.