Urban Infrastructure Development Using Non Woven Geotextile in Sarojini Nagar, Delhi

For the NBCC Sarojini Nagar Redevelopment Project in Delhi, Ocean Non Wovens supplied 36,000 SQM of Ocean Non Woven Geotextile 150 GSM (Polyester). The geotextile went into the pavement and foundation layers as a separation and filtration layer, to keep the soil stable and drainage working over the life of the development.

Project overview

• Project Name: NBCC Sarojini Nagar Redevelopment
• Location: Sarojini Nagar, Delhi
• Product Supplied: Ocean Non Woven Geotextile 150 GSM (Polyester)
• Quantity Used: 36,000 SQM
• Function: Separation and filtration in pavement and foundation layers

Site challenges

Urban redevelopment sites like Sarojini Nagar are tight. Limited working space restricts heavy equipment, so materials have to be quick to place and forgiving to handle.

The ground is rarely uniform either. Urban soils often contain mixed fill of varying strength. Without a separation layer, the aggregate in the pavement base is pushed down into the soil under traffic, and fines from the soil work up into the aggregate. Either way, the base loses thickness and drainage, and the pavement above ruts and cracks. During the Delhi monsoon, water entering a fine-grained subgrade softens it and speeds this up.

How the geotextile works

A non woven geotextile is a felt-like fabric of bonded polymer fibres. Laid between the subgrade and the aggregate, it does two jobs:

• Separation: It keeps the soil and the aggregate from intermixing, so the granular layer keeps its designed thickness and strength.
• Filtration: Water passes through the fabric while soil particles are held back, so water drains out of the subgrade without carrying fines into the base.

The same functions make non woven geotextiles standard in road and pavement construction, railway formations, drainage filters, foundation work and landfill protection layers. In India, the Indian Roads Congress covers their use in roads in IRC SP:59 (Guidelines for Use of Geosynthetics in Road Pavements and Associated Works), and MoRTH’s Specifications for Road and Bridge Works cover geosynthetics in Section 700.

A 150 GSM polyester non woven is a lighter grade. It suits separation and filtration where the subgrade is reasonably firm and the cover aggregate is not very coarse or angular. Softer ground, heavy construction traffic or large angular stone call for heavier grades with higher puncture and tear strength.

Installation and quality control

Key installation steps for a separation geotextile:

• Prepare a smooth, compacted subgrade free of protruding stones and debris
• Roll out the geotextile flat and without wrinkles
• Overlap adjacent rolls; firmer ground needs less overlap than soft ground
• Tip and spread aggregate from the covered area forward, so vehicles never drive directly on the fabric

Before the next layer goes down, inspections check that the geotextile is in position and undamaged, and that overlaps have not opened up.

Long-term performance

Polyester non woven geotextiles have good tensile strength, do not rot or biodegrade, and keep their filtration properties once buried and protected from sunlight. Where the separation layer stays intact, the pavement base keeps its thickness and drainage, which means less rutting and cracking and fewer repairs over the life of the pavement.

Ocean Non Wovens supplies non woven geotextiles and other geosynthetics to contractors, engineers and developers on infrastructure projects across India. For a similar application on a road project, see the case studies page.