The use of geosynthetics in the country’s infrastructure sector is growing steadily. Among these, geotextiles, geogrids and geomembranes are the three most commonly used products in terms of volume and value. With regard to their use in infrastructure, they find applications in sectors such as roads, railways, water, oil and gas, ports and waste handling.
Roads and railways
Globally, roads and railways are two key areas of application for geosynthetics. In road and railway projects, geosynthetics are used for erosion control, drainage, reinforcing soil walls, etc. The use of geosynthetics is particularly important in hilly terrains, areas with high soil erosion and those that are flood prone.
India currently has amongst the world’s largest road and railway networks. At present, a majority of the roads in the country are those with flexible pavements, which can benefit from geosynthetics for stabilisation of foundations. The central government has laid out huge investment plans for construction and upgradation of roads and railways, and this can boost demand for geosynthetics significantly. With many road projects being undertaken on the public-private partnership (PPP) model (which has a long concession period), the life-cycle benefits of the use of geosynthetics are reportedly expected to overweigh its higher initial cost. Further, new road projects awarded on an engineering, procurement and construction (EPC) basis have a built-in clause for maintenance of the road for a certain period (generally two to four years) after completion of construction. Thus, using geosynthetics can be an advantage as they are durable as well as easier to transport.
Many road projects in the country, particularly those in difficult soil terrains, have used geosynthetics. The material is also beneficial in regions that have limited supply of aggregates or sand as transportation of these raw materials over a long distance can be very costly. In comparison, geosynthetics are lighter and thus easier to transport.
Indian Railways (IR) has so far used geosynthetics only sparingly due to lack of Indian standards for these products. Recently though, IR has started looking at using geosynthetics for improving track quality for high speed trains, particularly in poor soil or rocky terrains. With IR’s increasing focus on high speed trains, portions of the existing track will need to be strengthened. This could be done with the help of geosynthetics. Its use is thus expected to rise with increased awareness of the advantages offered by these products.
The construction of runways and reinforcing pavements require extensive applications of geosynthetics to provide a smooth and even surface. Steep reinforced embankments or gabion walls are used to provide the flat area for runways and other airport infrastructure.
The runway at Kolkata airport was developed using non-woven geotextiles for runway base stabilisation. The main issue faced was drainage associated with the heavy monsoons. There was a need to minimise the erosive effect of water flowing under the pavement. The substrate comprised mixed materials (clays and sands) and displayed good compression resistance.
A non-woven geotextile capable of simultaneously serving the three purposes of separation, filtration and drainage was used to rebuild the runway. A blend of fibres of a specific linear density was used to achieve superior permeability performance on the geotextile surface. Drainage pipes were also installed every 20 metres to increase the drainage capacity of the system considering the heavy rainfall during the monsoons.
The need for environment-resilient infrastructure along the coastline will also drive the demand for geosynthetic products. Coastal areas are dynamic with unique geomechanical features such as soil instability and soft soils leading to a weak foundation. This creates the requirement for geosynthetics to provide soil stability. States that require significant investments in geosynthetics such as gabions and geobags are Odisha, Tamil Nadu, Maharashtra, Kerala and Andhra Pradesh that are likely to see significant development in the port sector.
Tunnel contractors are also experimenting with new and innovative materials such as geosynthetics and geomembranes. TechGeo PR30, a non-woven geotextile, manufactured by TechFab India Industries Limited has been used by the Delhi Metro Rail Corporation for tunnel works. The main functions of the geotextile were protection, separation and drainage between the top shotcrete lining and yellow geomembrane sheet.
The way forward
Growth in the country is expected to be driven by infrastructure projects in the road, railway, irrigation and water harvesting segments. The application of geosynthetics provides significant benefits over the project life-cycle in the form of speedier execution, lower maintenance and increased project life. Geosynthetics have a significant advantage over alternatives in regions with high soil erosion and extreme weather conditions. However, there are many inhibiting factors such as lower awareness, perception of lower durability and higher costs which result in the lower use of geosynthetics.