The construction sector in India has evolved over the years with the adoption of new technologies, materials and processes. Geosynthetics is one such product category that has gained traction. Largely manufactured from polymeric materials, these technical textile products are becoming more popular in infrastructure sectors and are being used to construct retaining walls and steep slopes, highways, airports, etc. Geosynthetics are a class of materials used in conjunction with soil to improve the overall performance. In general, they are planar products, made from polymeric material used with soil, rock, earth or other geotechnical engineering-related material, such as fly ash, as an integral part of a project structure or system.
The use of geosynthetics reduces the land requirement for projects and ensures the preservation of natural resources. These materials have been commonly accepted as durable, long-lasting and environmentally safe solutions for geotechnical engineering projects. A number of projects have reported cost savings of up to 30 per cent with the use of geosynthetics, which usually make up 3-5 per cent of the total project cost. Their use also minimises the routine repair and maintenance costs of a structure.
Roads and bridges
Geosynthetics are extensively used in road and bridge projects, making it possible to construct pavements in difficult terrains such as marshy stretches, in places with soft/organic deposits and in expansive soil areas. Geosynthetics can also be used for retaining the soil in steep embankment slopes in areas where right of way is restricted and even as reinforced soil walls for bridge approaches. These applications result in significant savings, improved performance and enhanced serviceability in the short term and long term.
National highway projects executed in Visakhapatnam, Vallarpadam, Tuticorin and Paradip have used geosynthetics. The construction of the major district road (MDR) No. 82 near Daund and MDR No. 65 (Jejrui-Morgon) in Pune used woven geotextiles for subgrade stabilisation. The development of the Gharni-Nitur-Nilanga section of State Highway (SH)-167 and the Taluka-Nilanga section in Maharashtra also used geosynthetics for subgrade stabilisation. Besides, the Lucknow-Sultanpur section of NH-56, Udaipur-Dungarpur-Shamlaji road, Biharsharif-Barbigha-Mokama section of NH-82, Rampur-Kathgodam highway, Koilwar-Bhojpur highway, and elevated road from Samrala Chowk to the Ludhiana municipal limit have used geosynthetics. A number of rural road projects being implemented under the Pradhan Mantri Gram Sadak Yojana have also used geosynthetics for construction. The huge pipeline of road projects in the country (especially with the launch of big-ticket programmes such as the Bharatmala Pariyojana) will provide a large market for geosynthetics.
As in the road sector, geosynthetics are utilised for rehabilitation and strengthening of existing formations in the railway sector. These are also used for separation and reinforcement thereby arresting pumping of fines from the sub-base into the ballast in order to prevent contamination of the ballast and minimising settlement of railway tracks (loss of track alignment and level). Geotextiles coupled with geogrids provide stabilisation and reinforcement to tracks. Indian Railways (IR) has so far used geosynthetics only sparingly due to lack of Indian standards for these products. IR has started using geosynthetics for improving track quality for high speed trains, particularly in difficult terrains. With IR’s increasing focus on high speed trains, portions of the existing track will need to be strengthened. This can be done with the help of geosynthetics. The use of geosynthetics is thus expected to grow with increased awareness about its advantages. Northeast Frontier Railway (NFR) has used geogrids in combination with geotextiles and sand layers for formation rehabilitation. The performance of a trial section has been satisfactory. For low density routes, geotextiles along with sand layers and brick soling (which is a method of laying bricks in brickwork) has been used in East Central Railway’s Sitamarhi-Darbhanga new line project.
In the airport sector, geosynthetics are used in the construction and extension of runways, and for reinforcing pavements. The runway at Kolkata airport was developed using non-woven geotextiles for runway base stabilisation. The main issue faced was drainage associated with heavy monsoons. There was a need to minimise the erosive effect of water flowing under the pavement. The substrate comprised mixed materials (clay and sand) and displayed good compression resistance. Besides, the development of Pakyong airport in Sikkim involved the use of geosynthetics. The runway was constructed by utilising huge amounts of earth cut from a hill to fill the valley side and get a level platform. A composite soil reinforcement system was used to retain and stabilise this fill, the height of which varies from 30 metres to 74 metres.
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.
Port development and dredging activity also involve the use of geosynthetics. Geotextiles are placed under rock ripraps or precast concrete blocks to prevent coastal erosion. They are also used as silt fences at construction sites to arrest soil particles from runoff water. Geotextile tubes are used in dredging activities while geocontainers are used for the disposal of potentially hazardous dredged materials offshore. For this, geotextile sheets are laid at the bottom of dump barges filled with dredged sediments and sewn. The containers are then transported to the disposal site and dumped using split hull barges. There is a need for environment-resilient infrastructure along India’s coastline. This would go a long way in the development of a market for geosynthetic products.
Geosynthetics are used in tunnel and track construction in urban rail projects such as the Delhi metro. They make it possible to use more effective construction methods thus saving time and money in comparison to traditional construction methods. Geotextiles are also used in constructing tunnels in hilly terrains. In the Pir Panjal tunnel located in the Pir Panjal range in Jammu & Kashmir, geotextiles and waterproofing membranes have been used. A waterproofing system made of geotextiles was also installed in the Rohtang tunnel. Geotextiles have also been used to mitigate the problem of slope failures and cracks on the portals of the Chenani Nashri tunnel that occurred because of water seepage.
Geosynthetics are also used in renewable energy projects for providing foundation support, stabilising concrete footings in wind and solar energy projects, and constructing mechanically stabilised earth walls and slopes. Geocells have been used to mitigate the problem of exposed foundations of 20 wind turbine generators at Mandsaur, Madhya Pradesh. The geocells helped in preventing surface soil erosion by confinement. For hydropower projects, geosynthetics are used for clay liners. Geomembranes are also used on the upstream face of earth fill, concrete and roller compacted dams. Geonets, geocomposites and geotextile drainage materials are used between the dam and the waterproofing geomembranes. For oil and gas companies, geosynthetics are used in the construction of paved and unpaved roads to access well sites and storage locations. Geomembrane liners are also used at well sites to control surface contamination and as secondary liners for storage tanks and tank farms.
Challenges and the way forward
Although the benefits provided by geosynthetics are being increasingly recognised, their use in infrastructure sectors in the country has not yet taken off. However, the government’s massive infrastructure development plans are expected to give a fillip to the demand for geosynthetics in India. Education in geosynthetics, both at academic institutes and at the industry level, is required for skilled manpower development. Further, the lack of specified standards for promoting geosynthetics use is another major challenge. Government authorities should issue guidelines for geotextile use in infrastructure projects. While the government is encouraging the use of geosynthetics, much more needs to be done to increase deployment.