Geosynthetics have proven to be a sustainable alternative to conventional construction materials across various infrastructure segments. Their primary application is in road construction for subgrade separation, reinforcement, drainage, filtration, soil stabilisation, etc. However, their use is no longer limited to these areas. It is now extended to the mining sector, railways and tunnels, and it is used as lining for solid waste landfills and for industrial projects such as ash treatment ponds in thermal power plants. These new prospects have boosted the use of specialised and technologically advanced geosynthetics. Some of these include geomembranes, geotextiles, geosynthetic clay liners, geogrids and geocomposites. These geosynthetic products minimise the impact on the environment by controlling soil erosion and reducing the need for extensive excavation and transportation of soil. As a result, they also enhance the performance of the infrastructure and minimise the need for maintenance.
Geomembranes
Geomembranes are the most common type of geosynthetic material being used in the infrastructure sectors. It is composed of thin continuous polymeric sheets of 0.5 mm to 3 mm thickness. They are produced by spraying asphalt, elastomer or polymer over geotextiles. One of its types is plastomeric geomembranes, which have a low permeability coefficient. Its application is seen in the waterproofing of surfaces in tunnels, airports, landfills, ash ponds in industries and wastewater treatment projects. It has been used in one such project of a landfill site at Gyaspur village in Ahmedabad, Gujarat. The project has been implemented by Maccaferri, wherein a geomembrane of 1.5 mm thickness is laid at the bottom and on the slopes. The membrane is composed of 97.5 per cent polyethylene and 2.5 per cent carbon black content. It also offers resistance to ultraviolet rays, which improves its shelf life.
Another project is the thermal plant of Thermal Powertech Corporation India Limited, where geomembrane MacLine SDH high density polyethylene (HDPE) has been used by Maccaferri. It has a thickness of 1 mm and acts as an impermeable liner. It has been applied on the slopes and the bed of the plant’s ash ponds.
In another development, geomembranes have been used for the drainage system in the Kempegowda International Airport in Bengaluru. In this project, the polyvinyl chloride drainage pipes have been wrapped in these membranes, called geodrain membranes. These are then installed in pre-drilled holes in the embankment at a slope. This drainage system helps in reducing the hydrostatic pressure in the embankment, while the geodrain membrane prevents the leaching of soil and fine material.
Geotextiles
Geotextile is a technical textile, primarily used in the reinforcement of embankments in construction projects. It is categorised into three types – knitted, woven and non-woven geotextiles. The knitted type is made by interlocking a series of loops of yarn together, the woven type has interlaced flat or round strands of geotextile at right angles and the non-woven type is thermally or chemically bonded or produced through the technique of needle-punching. Several active measures are being undertaken by the Ministry of Textiles to ensure good quality of geotextiles. In April 2023, the ministry launched quality control orders for 31 items consisting of 19 geotextiles. Some of these are open-weave coir Bhoovastra geotextiles used in subgrade separation in pavement structures and geotextiles used in subsurface drainage applications, permanent erosion control in hard armour systems, etc. Additionally, it plans to set up a testing laboratory for geotextiles at the National Institute of Technology Karnataka, in Surathkal. The laboratory will have 21 advanced equipment for elemental tests on geotextile fabric and model testing on reinforced earth under dynamic loading. It has also planned to implement compulsory quality control measures for various products including needle-punched, non-woven, polypropylene multifilament woven, jute geotextiles and HDPE in the future.
Furthermore, natural fibres are also being woven into geotextiles to minimise their environmental impact. These biodegradable geosynthetics are gaining traction as they decompose naturally. One such geotextile is the coir geotextile, which is made from coir yarn. Its application is also witnessing a push in the mining sector. For instance, the Kerala State Coir Corporation will supply coir geotextiles to mines in Odisha. In June 2023, it received an order for geotextiles from Geetarani Mohanty Raikela Iron Ore Mines. It would undertake a pilot project worth Rs 1 million for its application in the mines. This material is highly durable and resistant to rots, moulds and moisture.
Geosynthetic clay liners and geogrids
Geosynthetic clay liners are another type of geosynthetic technology that is gaining attention. They are prefabricated rolls, composed mainly of two layers of non-woven geotextiles, with an intermediate layer of sodium bentonite powder. Their application ranges from landfill liners, canal lining, stormwater impoundments, wetlands, highways, civil construction, mines, etc. These liners have been used in the first scientifically engineered landfill in
Tehkhand, Delhi. Under the project, 2 metre high embankments have been created around the landfill and covered with layers of these liners on one side. The project work has been completed by the Municipal Corporation of Delhi and the landfill will be used to dispose of the ash generated in two waste-to-energy plants in Okhla and Tehkhand in Delhi.
The use of geogrids is another technological development in geosynthetics. Geogrids are single or multi layer materials made from extruding and stretching HDPE or by weaving and coating high-tenacity polyester yarns or glass fibre with an appropriate coating. This creates a grid structure that has large openings and aids in enhancing the bond with the soil or aggregate. This type of geosynthetic is most suitable for reinforcement and stabilisation of soil and aggregate, given its high tensile strength. It has two sub types, uniaxial and biaxial. The uniaxial geogrids are mainly used in slope reinforcement, landfill expansion projects, retaining wall reinforcement and railway embankments, whereas the biaxial type has multiple applications such as the construction of access roads and haul roads in mines; heavy-duty pavement such as container yards, port areas, airports and large axle loads; and stabilisation of railway track beds. One such project where the biaxial geogrid has been used is the Agartala Sabroom Railway Line. In this, a biaxial geogrid product called MacGrid EG 30S was used with woven multifilament geotextile in between subgrade material. Further, the Bureau of Indian Standards has established stringent standards and certification processes to ensure the quality and performance of geogrids.
Other technologies
Some of the other technological developments in geosynthetic products include geocomposites, geonets and geocells, among others. Many innovative geocomposite products have been introduced by Strata Geosystems such as StrataDrain drainage composite and StrataGrid geocomposites. They are being deployed in the ongoing stabilisation of Kuber Tila at Ram Mandir in Ayodhya. Similarly, the use of geonets has been successful in strengthening foundation works and roads. It has been used for improving the delta and road structures in Assam with its application in the construction of the first green road of 183 km in Goalpara. Moreover, the three-dimensional, permeable, polymeric honeycomb structures of geocells are also being explored for flexible pavements, sub-ballast and ballast reinforcement in railways and basal reinforcement.
The way forward
The Indian geosynthetic market is expected to expand manyfold in the coming future. As an important component of this market, geotextiles would also witness a huge push. The global demand for geotextiles is on the rise and, therefore, the Ministry of Commerce is aiming to improve its manufacturing and supply chain. Similarly, the government’s thrust on infrastructural growth in 2024-25 will create a bigger market for other geosynthetic products. There would be greater emphasis on their research and development. Furthermore, the integration of nanotechnology with geosynthetics would open up a huge potential for the infrastructure sector. For instance, nanocoatings can provide chemical resistance to geomembranes while nanofibres can make geotextiles more lightweight. The installation of geosynthetic products would also be revolutionised with robotic deployment systems. They would help in minimising human errors and enhancing safety levels at hazardous construction sites.