Can geosynthetics help in our efforts toward conserving resources and the environment?
The world is undergoing tremendous change due to increasing population, industrialization, and urbanization, leading to rapid resource shifts (1). There is growing global agreement on the need to achieve sustainable development to improve the lives of millions of people in low and middle-income countries by providing clean water, sanitation, energy, and transport solutions (2).
Over the past few years, many studies have focused on investigating the benefits of geosynthetic solutions as economical and environmentally friendly alternatives to nonrenewable earth resources in civil engineering projects (3, 4, 5). In this regard, a study in the International Geosynthetics Society mentioned the role geosynthetics could play in achieving United Nations sustainable development goals 6, 9, 12, 13, and 17, which refer to clean water and sanitation; industry, innovation, and infrastructure; responsible consumption and production; climate action; and partnerships for the goals, respectively (6).
This article explores geosynthetics’ environmental and economic benefits in landfills, reservoirs, and mining.
Types and functions of geosynthetics for conserving resources
Generally, geosynthetics are divided into six groups based on their functionality (see Figure 1): moisture barrier, erosion, control drainage, filtration, reinforcement, and separation (1). As a result, various families of geosynthetics have evolved, including geotextiles, geomembranes, geogrids, geonets, geocomposites, and others.
Tables 1 and 2 describe these geosynthetic functions and families in brief. On the other hand, the long-term performance of geosynthetics is an obvious result of the material type used in producing them. A study on this issue has highlighted the long-term degradation mechanism of geosynthetics made from various resins, as shown in Table 3 (7).
Geosynthetics landfill and slope applications
Landslides involve various ground motions resulting in a movement of mass and include rockfall, deep slope collapse, and shallow debris flows. Typically, landslides are controlled by enhancing drainage conditions, planting vegetation on slopes, constructing some retaining structures, and utilizing ground-improvement techniques (8, 9, 10). For this reason, geosynthetics are highly preferred in projects involving embankments constructed on soft foundation soils. These materials are cost-effective alternatives to conventional foundation-stabilization techniques, including excavation, dewatering, thick stabilization aggregate layers, and chemical stabilization (11).
Geosynthetic layers serve as reinforcements to expedite the consolidation process in soft soils. Moreover, these reinforcements decrease filler consumption due to minimizing or avoiding local failure mechanisms resulting from the construction equipment used to transport, spread, and compact filling materials (12). In addition to reinforcing geogrids, a random distribution of fibers within the soil mass or piled embankments can considerably increase the subgrade materials’ strength (13).
Slope stability is another area where geosynthetics are widely applied for improvement, providing a new level of efficiency to the design and construction of slopes and retaining walls with geogrids. Geosynthetic reinforced walls have become ubiquitous and are widely used worldwide (14, 15). These reinforced slopes comprise compacted fill embankments that integrate horizontal geosynthetic layers as tensile reinforcement to improve structural stability. Additionally, using geosynthetics for stabilizing slopes reduces the size of earthworks by modifying their shape and even permits the usage of soils with average mechanical properties. In this regard, woven and nonwoven geotextiles and geogrids are increasingly used to reinforce steep slopes (16).
Geosynthetics hydraulic applications
Geomembranes have been one of the most significant inventions in the field of hydraulic structures in the last fifty years due to their vital role in ensuring safe and eco-friendly projects (1). Typically, geomembranes are used worldwide in waterproofing various dam types, including masonry dams, embankment dams, concrete dams, and roller-compacted concrete dams (17).
Throughout the service life of typical concrete dams, the upstream concrete deteriorates, increasing leaks. Composite geomembranes consisting of a geomembrane and a geotextile are the most frequently utilized geosynthetics in constructing new dams and repairing aging concrete dams. Generally, the geomembrane serves as the lining system. At the same time, the geotextile strengthens and protects the geomembrane from mechanical damage caused by the irregularities in the supporting medium and provides drainage behind the geomembrane (17, 18).
In embankment dams, geomembranes enhance dams’ safety by reinforcing the lining system. In roller-compacted concrete dams, geomembranes are primarily used in new construction to line the entire upstream face of the dam. The dam’s mass provides stability in these dams, while the upstream geomembrane renders the structure watertight. A previous study has shown that using geomembrane material and concrete can significantly control the seepage issue in structures compared with bare concrete solutions, as shown in Figure 2-a (19).
Another important geosynthetic hydraulic application is canal leakage prevention through geomembrane lining (19). Previous measurements have shown that leakage in geomembrane-lined canals is ten times less than in canals with just a cement lining. As a result, geomembranes could be seen as a repairing material for cement-lined canals (1, 20). In addition, geomembrane systems were successfully installed as waterproofing solutions in tunnels and reservoirs (21, 22). In these projects, the geomembrane sheets are backed by a drainage structure to prevent water accumulation and discharge water that causes an inward pressure. This type of backpressure on regular coatings and poorly attached lining systems can cause an uplift of the lining system (23).
Geosynthetics may also be used to construct assemblies for dewatering waste and contaminated sediments (24, 25) and freshwater reservoirs to minimize evaporation, reduce cleaning maintenance, control algae development, and decrease chlorine utilization by covering the water surface (26).
Geosynthetic mining applications
Generally, the goal of introducing geosynthetic barriers to a modern mining operation is to reduce the environmental risks caused by contamination moving off-site and improve the mines’ ability to recover water for reuse or product extraction (27). Liners are made to meet requirements similar to bottom-lining systems in landfills, emphasizing the chemical and mechanical conditions seen in mining operations. As a result, geosynthetic materials are increasingly widely employed in heap leach pads, waste rock or overburden storage facilities, tailings storage facilities, and lined ponds and channels (28, 29).
Environmental Benefits of Geosynthetics
Geosynthetics provide a wide range of environmental benefits and are considered to achieve the sustainable development goals of the United Nations (6). For instance, multiple studies have demonstrated the possibility of producing sustainable geosynthetic systems incorporating partial non-biodegradable waste replacement (30, 31). In this regard, recycled construction and demolition wastes in geosynthetic reinforced structures have been utilized previously (32, 33, 34).
Furthermore, the usage of waste tires with geosynthetics as a drainage system of landfills has been investigated before (35, 36). In contrast, drainage cores have been produced from a combination of geocomposites and polyethylene terephthalate recycled from old bottles (37). On the other hand, geosynthetic solutions are usually associated with a considerable reduction in greenhouse gases and CO2 emissions (6). A brief illustration of the importance of geosynthetics to pollution and embodied carbon control is presented in Table 4. In addition to the benefits above, geosynthetics contribute to soil quality protection and sustainable food production (13, 18, 38) and improve animals’ life by producing better animal-intended structures, such as in the case of fish farming (26, 39).
Economic Benefits and Conserving Resources
Compared with traditional solutions based on soil, concrete, and steel, utilizing geosynthetics in civil engineering applications frequently provides financial benefits by reducing the cost of imported materials, reducing waste, and generally providing more efficient use of resources (40).
For instance, in the roadway, geosynthetics are responsible for reducing the amount of soil, shortening the construction duration, and increasing the project’s long-term performance, ultimately reducing the cost (1). Additionally, geotextile filters decrease the size of edge-drain trenches, saving excavation and filter material volumes and thus reducing the cost of the project (3). Furthermore, the material cost difference of the geosynthetics utilized in embankment reinforcement and waste containment systems improves the economic aspects of such projects (41). A brief numerical illustration of the geosynthetics’ economic benefits is shown in Figure 2.
This report has focused on exploring geosynthetics’ environmental and economic benefits in landfills, reservoirs, and mining. Within the context of the article, different aspects, such as the types, functions, life cycle assessment, and cost efficiency of various geosynthetics, have been discussed and highlighted. Based on the statements above, the following conclusions are drawn:
- Many different types of geosynthetics can be used across various civil engineering projects, including geotechnical and hydraulic projects.
- Geosynthetics are excellent stabilizers of soil slopes and embankments.
- Geomembranes are effective waterproofing layers typically used in landfills, dams, tunnels, and reservoirs.
- A combination of geosynthetics and recycled materials can be used to control the issue of non-biodegradable wastes.
- Geosynthetics control pollution and greenhouse gases in various civil engineering projects.
- The utilization of geosynthetics is associated with cost efficiency due to their capability to reduce material usage in various construction scenarios.
Tables and Figures
Table 1. Descriptions of the main geosynthetics functions (42).
Table 2. Descriptions of the main geosynthetics families (43).
Table 3. Long-term degradation mechanism of geosynthetics with various types of resins (7).
Table 4. Life cycle assessment of various geosynthetic solutions (6).
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