**1. Introduction**

#### *1.1. General Considerations*

Geotextiles, a group of high-performance materials, have grown during the last decades into needful auxiliaries when it comes to infrastructure, soil, construction, agriculture and environmental applications. Although geotextiles made of synthetic fibers (geosynthetics) are considered a modern achievement, the basic concept dates back to ancient times when textiles consisting of locally available natural fibers were employed to increase the stability of roads and soils [1–3]. Nowadays, whether it is the stabilization of soil in arid regions [4] or the river banks and seafronts (in tidal areas or harbor infrastructure) [5,6], ground reinforcement for civil infrastructure [7–9] or filtration of water excess in farmlands and flood protection [10–12], hill slopes stabilization and drainage [13] or even the reinforcement of airstrips under the tarmac layer [14,15], geotextiles are successfully performing in civil engineering and agriculture and becoming an increasingly viable alternative in many other applications.

Geosynthetics [16], the geotextiles made of synthetic polymers (such as PP, PE, PET and PVC) manufactured as fibers, are used in notably large amounts as the polymer production is cost-effective and the corresponding fibers are easily obtained by melt spinning using already existing technology. Their remarkable mechanical properties (mainly tensile

**Citation:** Tanas˘a, F.; Nechifor, M.; Ignat, M.-E.; Teac˘a, C.-A. Geotextiles—A Versatile Tool for Environmental Sensitive Applications in Geotechnical Engineering. *Textiles* **2022**, *2*, 189–208. https://doi.org/10.3390/textiles 2020011

Academic Editor: Laurent Dufossé

Received: 8 March 2022 Accepted: 6 April 2022 Published: 8 April 2022

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strength), durability and hydrophobicity make them fit for geotechnical engineering applications, such as the improvement of the bearing capacity of the ground in preparation of construction sites [17]. On the other hand, some polymers require a supplemental employ of additives, prior to their spinning, in order to improve or customize some of their properties with respect to their further applications. Thus, the UV resistance of PE fibers is significantly increased by adding carbon black as a stabilizer to the pristine polymer [18], while composites based on epoxy resins or unsaturated polyesters have achieved improved thermal and mechanical characteristics upon incorporation of glass fibers or carbon fibers in their formulations [19]. The main drawback of the long-term use of geosynthetics is their degradation under environmental conditions (humidity, acid/base or salty atmosphere, pollutants, UV–vis irradiation, wind and particle abrasion, microorganisms attack, temperature variation and seasonal freeze–thaw cycles, etc.) [20–22]. Nevertheless, the lifetime of geosynthetics and their operating performance depend directly on the chemical and structural stability of the synthetic polymers in their composition [23]. The advanced geosynthetics are, thus, designed so as to have better stability during their service time. Even more, with the considerable help of intelligent geotextiles which have sensors and/or sensing-and-actuating devices incorporated in their structure, it was possible to first discern chemical and/or physical changes of materials and to identify precociously the imminent material failure, whether a brittle or ductile failure.

In recent decades, considering the growing interest in environmental protection and sustainable development based on using renewable resources and the recovery and recycling of waste of various origins, the use of natural fibers-based geotextiles is a viable alternative, despite their limited-life service owing to their biodegradability. In addition to this feature, their low cost, good mechanical properties and large-scale accessibility recommend them for geo-engineering applications, such as soil stabilization and reinforcement, and erosion control [13,24–26]. Moreover, natural fibers (such as sisal, kenaf, hemp, jute, ramie and coir, etc.) employed for geotextiles are locally available which counterbalances their properties' variation (sometimes within large limits). Therefore, complex approaches have been developed in order to improve their properties and include (but are not limited to) fiber surface modification by various treatments [27], use of special additives or degradable thermoplastic biopolymers [28], employment of hybrid yarns made of natural and synthetic fibers [29,30], etc. Recently, it was assessed that natural geotextiles are able to replace geosynthetics in almost 50% of their applications [26].
