Dark-coloured, netted fabrics draped on concrete panels are all over the vertical structures coming up on the 42.6 km stretch from Chengapalli to Neelambur. Coimbatore is not only seeing the much-needed widening (six-lane) of NH 47 from Chengapalli to Neelambur but also modern materials used in the construction. “Geo synthetic reinforcement fabrics” are used to reinforce the earth walls in this project.
The National Highways Authority of India (NHAI) has taken up widening of the high-traffic National Highways road into a six-lane one at a total cost of Rs. 852 crore and the work is carried out by IVRCL Infrastructure. The road connects Coimbatore to Tirupur and Erode districts.
According to NHAI Project Director P. Manivannan, geo fabrics are used for reinforced earth walls. The fabrics have geo grids and are used to reinforce the earth and keep the structure vertical. These are designed to take the load and prevent the wall from tilting. Earlier, retaining walls made of concrete were constructed. Use of geo fabrics instead has made the work easier and faster and reduced the costs too. It gives better aesthetics to the road.
The fabric used here is about 1.3 metres wide. Usually, when a road is designed, the width and thickness of the grid and fabric is specified for each stretch. Pre-cast concrete panels with hooks are erected and the fabric is connected to these hooks with galvanised coated steel rods. Earth is rolled on top of the fabric. These are also used below the ground level, depending on the soil, to strengthen the foundation, he says.
These fabrics are mostly used in rail over bridges and flyovers where there are high embankments. The life of the fabric is long and these reduce the width of the land required for the works. The fabric can be used when there are materials with lesser bearing ratio, he says. The NHAI is using the fabric in several projects in the country for the last seven years.
