Modern Materials

Geosynthetic products and their uses

Geosynthetics have a wide range of applications. Almost every large-scale infrastructure project requires some degree of geosynthetic material. As a result, geosynthetics represent a distinct class of products. Modern materials such as geosynthetics guarantee the quality, durability and long-term sustainability of infrastructure. Their polymeric nature makes them an ideal choice for applications requiring a high level of durability, giving them an advantage over other alternative solutions. There are several geosynthetic solutions available to efficiently tackle difficulties in every building project, including separation, drainage, filtration, reinforcement and protection. In addition, geosynthetics have the potential to significantly reduce capital and operating expenses, as well as construction time. The key materials required for geosynthetics include polyethylene, polypropylene, polyvinyl chloride and ethylene propylene diene monomer.

India is undergoing a massive infrastructural transition as a fast growing country, with tre­me­n­dous growth in trains, roads, power, and wa­ter resources, among other sectors. It is critical that these facilities are long-lasting in order to avert environmental disasters and land scarcity.

With climate change and an ever-increasing carbon footprint, geosynthetic goods provide sustainable solutions, giving them an advantage over traditional construction methods. Geosyn­the­tic-based projects can be efficiently completed using significantly less concrete steel and hence, earth soil. They also provide unique benefits that have the potential to significantly ev­ol­­ve engineering processes in response to ap­pli­ca­tion-specific difficulties. Without a doubt, geo­syn­thetics will be critical in accomplishing the country’s aggressive infrastructure timelines and budgets in the coming years.

They are further divided into geotextiles, geocomposites, geogrids, geomembranes, geocells, geonets and geofoams based on their physical properties and applications. Their role includes execution of five key functions – separation, reinforcement, filtration, drainage and containment.

Key geosynthetic products

Geotextiles: Geotextiles are porous polypropylene or polyester fabrics. They are used in civil engineering for erosion control, soil stabilisati­on, reinforcement, separation and drain­age. ­Geo­textiles enhance the capabilities of soil fills in civil construction projects. They improve the controllability of difficult soils, enabling development in areas that would be unsuitable otherwise. They are an excellent choice for a wide variety of infrastructure projects, including highways, harbours, landfills, drainage structures, and other civil works.

Geotextiles are further classified as woven fabrics, non-woven fabrics, and knitted fabrics. Woven geotextile fabrics are produced by interlacing flat or round strands of material at right angles. Non-woven geotextile fabrics, which re­semble felt, are frequently produced via needle-punching, a process in which barbed needles repeatedly press through layers of fibrous webs of material. This repetitive action results in extremely permeable textiles, also referred to as filter textiles. Geotextiles are advantage­ous in highway, railway and port projects be­cau­se they minimise maintenance costs and extend the life of the infrastructure asset. The road sector in India is a significant consumer of geotextiles. On January 18, 2022, the Ministry of Tex­tiles approved 20 key research projects totalling Rs 300 million in the areas of specialised fibres and geotextiles. These strategic research initiatives are under the government’s flagship Na­tio­nal Technical Textiles Mission. Among the 20 research projects, four geotextile (infrastructure) projects have been approved.

Woven geotextiles have been utilised in the Tapi River embankment and flood protection works in Gujarat; raising and strengthening the retaining wall in Surat; dredging and reclamation works at the container terminal in Mum­bai; coastal protection work of Valsad, Surat and Navsari; reinforced earth (RE) walls for the Barwa Adda Expressway; and in laning, im­pro­ving and strengthening various highways roads in states like Maharashtra, Ta­mil Na­du, Jammu & Kashmir, Gujarat, Jharkh­and and Karnataka. Meanwhile, non-woven textiles have been used in for in surface drainage in Sangli (Maha­ra­shtra), and new IIT Indore (Ma­dhya Pradesh); water quality improvement in the Min­dho­la river, Surat; protection of geomembrane (cushioning) in landfills in Maharashtra and Gujarat; and waste management in Vapi, Gujarat.

Geogrids: Geogrids are typically composed of polymers such as polyester, polyethylene, or polypropylene and are used to strengthen soils and similar materials. Geogrids are frequently used to support retaining walls and subcases or subsoil beneath highways and constructions. While geogrids are typically utilised for reinforcement, some are also used for asphalt overlay and waterproofing, as well as separation and stabilisation. Geogrids can also be utilised as gabions and sheet anchors, inserted between geotextiles and geomembranes, or used to create mattresses for filling or embanking soft soils. Geogrids are classified into two types – uniaxial and biaxial. Uniaxial geogrids are primarily used for slope reinforcement, retaining wall reinforcement, landfill expansion projects, and railway embankments. The purpose of biaxial geogrids is to transmit loads uniformly to the underlying weak strata with low SBC as reinforcement beneath roads and foundations.

There are a number of successful Indian biaxial projects, including roads and warehouse land strengthening in Maharashtra and Gujarat, as well as the foundation work for Western Rail­way in Ahmedabad. Roads and railway overbrid­ges/RE walls in Assam, Bihar, Gujarat, Ma­ha­­rash­tra, Tamil Nadu, Haryana, Uttar Pra­desh, An­dhra Pradesh, Rajasthan, Himachal Pradesh, Karnataka, and Chhattisgarh have all been constructed utilising uniaxial geogrids.

Geofoams: Geofoams are blocks or slabs formed when polystyrene foam is expanded to form a network of closed, gas-filled cells. They are very light and resistant to hostile environments. They are frequently utilised in fill applications where a light material is required to alleviate stresses on underlying soils or lateral pressures on retaining walls, abutments, or

fo­­un­dations. Geofoam is an excellent thermal insulator and can help save money on heating and cooling costs. It is also used to fill the interiors of building walls, as well as the roofing and ground constructions of all sorts of reside­n­tial and commercial structures.

Geomembranes: Geomembranes are synthetic membrane liners with a thickness of 0.5-3 mm that are used to regulate fluid migration within a man-made structure, project, or system. They are composed of relatively thin continuous polymeric sheets that are occasionally created by spraying asphalt, elastomer, or polymer over geotextiles. Geomembranes are utilised in environmental, hydraulic, transportation, oil and gas, and waste management applications.

The most typical applications of geomembrane are liners for potable or reserve water (such as safe shutdown of nuclear facili­ti­es), liners for waste liquids (such as sewage sludge), liners for radioactive or hazardous waste liquid, and as waterproofing liners within tunnels and pipelines. Geomembranes are more expensive per unit than other geosynthetic produc­ts. ­Geomembranes have previously been utilised as a pond liner for raw reservoirs in Andhra Pra­desh and Maharashtra; as a mining evaporation pond for a zinc mine in Madhya Pradesh; and as a landfill/waste management material in the states of Maharashtra, Gujarat and Karnataka.

Geonets: Geonets are typically produced by a continuous parallel set of polymeric ribs arranged at acute angles to one another to form a net-like structure. They are formed by pressing thermoplastic polymers or by welding threads/bands together. Their intended role is entirely contained inside the drainage region, where they are utilised to transport a variety of fluids. These products serve a variety of purposes. The primary objective is to separate the two soils. The purpose of separating two distinct ground structures is to keep granular grounds functional. Due to pollution and fine-grained ground, these two types of floor structures can lose their properties. Another rationale for using geonet is to reinforce the ground. Due to the friction and locking effects of these items, they increase the carrying capacity of the current system.

Geonets are mostly employed in landfills, foundation walls, methane highways, and asphalt concrete pavements, as well as for erosion and drainage control. Despite the mutual penetration of constructive layers, geonet en­ables the jamming effect of structural fill mate­rial in meshes, allowing for horizontal slide control. Geonets’ hardness features enable them to withstand substantial loads. These innova­tive products can be deployed at any stage of development to improve road design, conserve water, manage evaporation, decrease erosion, strengthen the resilience of structures, and extend their life. Furthermore, geonets are routinely laminated with geotextiles on one or both surfaces, culminating drainage geocomposites. In addition, they were used to lay the foundation for the S.W. drains and sewer lines in Dronagiri (CIDCO, Mumbai).

Geopipes: They are polymeric pipes with perforated or solid walls that are used to drain liquids and gases. In some situations, a geotextile filter is wrapped around the perforated pipe. These pipes are typically used to collect lea­chate. They are also used in situations involving strong compressive loads. Geopipes can be utilised in landfills to aid the collection and rapid drainage of leachate to a sump and treatment system. They are used in water and gas distribution, sewer and wastewater treatment, oil and gas production, industrial and mining purposes, power and communications, duct and irrigation syste­ms. ­They are also referred to as “buried plastic pipe”.

Geosynthetic clay liners: Geosynthetic clay liners are prefabricated rolls composed mainly of two layers of non-woven geotextiles with an intermediate layer of sodium bentonite powder. The two geotextile layers are sewn together (needle-punched non-woven), resulting in a perfectly stable mat with high internal shear resistance. When the sodium bentonite in the mat comes in contact with water, it expands and forms a waterproof mineral layer. Liners made of geosynthetic clay are frequently used as hydraulic barriers for water, leachate, and other liquids and gases. They are also utilised in place of compacted clay liners or geomembranes, or in combination with more typical liner materials. Geosynthetic clay liners are frequently used to line canals, storm water impoundments, and wetlands, as landfill liners and capping, for secondary containment, and in highway and civil construction, as well as mines. Geosynthetic clay liners have been previously used as pond liners in Jammu & Kashmir.

Geocomposites: Geocomposites are geosynthetics that combine two or more types of geosynthetics, such as geotextile-geonet, geo­t­extile-geogrid and geonet-geomembrane. In terms of functionality, interface friction angles and installation speed, these combinations exceed individual geosynthetic layers. Typi­cally, they are used for filtration, separation, streng­thening, drainage and containment. Geocom­p­o­sites are hybrid systems that can be used to solve specific soil, rock, waste and liquid-related challenges. The geocomposites market is classified primarily into three segments – drainage, containment, and others. The largest section is drainage, which includes civil and ro­ad construction, trench drains, pavement base course or edge drains, railway and road tunnels, rooftops, retaining walls, and bridge abutments. They have been used as geomats in many projects. For example, geotextile mattre­ss composites (upper green non-woven layer and lower black woven layer) have been utilis­ed to manage erosion and flooding, as well as to protect banks and dykes from river erosion in Majuli and the Brahma­putra river.

Geocells: Geocells, or cellular confinement systems, are three-dimensional structures made of ultrasonically welded high density polyethylene strips that expand to form a honeycomb-like structure on-site. They are intended to contain soil, gravel, or other fill material within their maze of cells or pockets and may be po­rous to allow water to flow through them. They are used to stabilise slopes with soft subgrades and limit erosion in channels. Chemical resistance, ageing resistance, ex­ce­llent durability, and intrinsic flexibility are only a few of the key characteristics of geo­cells. Geocells have been used in the raw water reservoir for the OGT in Mallavaram, Andhra Pradesh.

Outlook

Geosynthetics provide some of the most desired features of durability and environment friendliness with the added benefits of minimising accidents, extending the life of structures, and promoting resource efficiency. The growing demand for geosynthetics is mostly a result of increased investment in infrastructure construction and the growing worldwide concern about waste and water management. Technological advancements and increased consumer demand for sustainable products have also created opportunities in the geosynthetics market.

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