How Geosynthetics Are Used in Delhi-Mumbai Expressway Construction

The Delhi-Mumbai Expressway is the longest expressway India has built: about 1,386 kilometres (early project documents quoted 1,350) across six states, at a cost of roughly one lakh crore rupees. It is a greenfield, eight-lane road, and once it is fully open the Delhi to Mumbai drive is expected to fall from about 24 hours to around twelve. Under the carriageway, its interchange walls and its embankment slopes sit layers of geosynthetics: the polymer grids, fabrics, cells and membranes that reinforce, separate, drain and protect the ground. This article explains where each type is used on a corridor like this one and why.

Project Overview: A Corridor Built for the Future

Greenfield means the alignment was cut through new ground rather than widened from an existing road, so planners could set gentle gradients, wide medians and grade separations from the first survey line. The route passes through Delhi, Haryana, Rajasthan, Madhya Pradesh, Gujarat and Maharashtra, linking the national capital region to Mumbai via cities such as Jaipur, Kota, Vadodara and Surat. It has been opening in sections since the Delhi-Dausa-Lalsot stretch was inaugurated in February 2023.

A road this long crosses very different ground: the dry sandy soils of Rajasthan, the expansive black cotton soils of the Malwa region in Madhya Pradesh, and the high-rainfall coastal belt of south Gujarat and Maharashtra. Geosynthetics let engineers build on all of these with locally available fill, fewer truckloads of quarried aggregate and less concrete.

Why Geosynthetics Are Central to Expressway Construction

An expressway with continuous grade separation needs far more steep embankment, retaining structure and approach ramp than an ordinary highway, and those slopes have to stay stable for decades under heavy, fast traffic. Building all of it in reinforced concrete with imported aggregate would be slow and expensive. Geosynthetics reinforce soil so it can stand steeper and carry more, separate and drain weak ground, and hold slope surfaces against erosion, which lets compacted fill and a light polymer layer do work that would otherwise need concrete and steel.

Indian practice covers each use. IRC:SP:59 gives guidelines for geosynthetics in road pavements and associated works, IRC:113 covers geosynthetic reinforced embankments on soft subsoils, and Section 700 of the MoRTH Specifications for Road and Bridge Works sets material and construction requirements. Test methods come mainly from ASTM and ISO, with Geosynthetic Institute (GRI) specifications for products such as HDPE geomembranes.

Retaining Wall Case Study: The Geosynthetic Reinforced Earth Wall

Every interchange, flyover approach, vehicular underpass and ramp has to hold earth back at a steep face. On NHAI corridors, including this one, that is usually done with a reinforced soil wall rather than a reinforced cement concrete retaining wall.

Soil is strong in compression and weak in tension. Layers of high-strength geogrid are laid horizontally in compacted engineered fill at set vertical spacings, and friction and interlock with the fill transfer load into the grid, so the reinforced block behaves as one gravity mass. A facing of precast concrete panels, modular blocks or a vegetated fascia gives the vertical or near-vertical face. Such a wall can rise many metres, carry live traffic surcharge, and tolerate ground movements that would crack a rigid concrete wall.

The wall rises in compacted lifts instead of waiting on formwork and curing, so it is quicker to build. It uses much less cement and steel, it tolerates differential settlement, and it can use suitable local fill, which cuts cost and haulage. On a project with a tight opening schedule, that takes one of the slowest, most material-heavy items off the critical path.

Erosion Control: Geocells on Expressway Slopes

Tall embankments and deep cuttings expose large areas of bare soil to the monsoon. Unprotected slopes erode, gully and eventually slump, which threatens the carriageway and blocks drains. A common answer is the geocell.

A geocell is a three-dimensional honeycomb of high-density polyethylene strips, ultrasonically welded so that the panel opens into a network of interconnected cells when stretched. Pinned to a prepared slope and filled with topsoil or aggregate, it holds the surface material inside the cell walls so runoff cannot carry it away. The confined topsoil keeps moisture and nutrients where vegetation can root, and the filled panel spreads load like a flexible mattress. Slopes protected this way need far less repair after each monsoon than bare ones.

On expressway projects, geocells are used to green and stabilise embankment faces, to line channels and drains against scour, and, filled with aggregate or concrete, to support loads over weak ground. The confined layer acts as a semi-rigid mattress, so the same product can also reinforce a road base.

Separation and Filtration: Geotextiles Beneath the Pavement

A thin geotextile between the subgrade and the pavement layers stops soft subgrade soil from pumping up into the granular base and stops the aggregate from punching down into the soil. Without it, the two layers mix under traffic, the base loses strength and the pavement fails before its design life.

The same fabric filters and drains, letting water out while holding soil particles back, which relieves the pore-water pressure that softens subgrades and undermines shoulders. That matters most on the flood-prone and high-rainfall stretches. Woven and non-woven geotextiles are specified by apparent opening size, permittivity and tensile strength, tested to ASTM methods and the IRC/MoRTH requirements, and matched to the soil they protect.

Geomembranes at Water Crossings

Where the road runs beside or across water bodies, canals and stormwater channels, geomembranes are used. An HDPE geomembrane is a continuous low-permeability sheet that keeps water from seeping into and softening the road structure and keeps contaminated runoff away from groundwater. It is used to line channels, protect embankment cores and waterproof crossings. HDPE geomembrane properties are specified in GRI-GM13 from the Geosynthetic Institute and IS 16352 from the Bureau of Indian Standards.

Carbon Savings: The Sustainability Case

Cement and steel are two of the most carbon-intensive materials in construction. A reinforced soil wall relies mainly on compacted local fill and a modest weight of polymer reinforcement, so it needs far less of both than a concrete cantilever wall of the same height, and its embodied carbon is correspondingly lower.

Other savings add up along the corridor. Geogrids that allow a thinner aggregate layer reduce the quarried stone that has to be mined and hauled. Walls and slopes built from local fill need fewer truck movements. Faster construction shortens the period of site emissions. Vegetated, geocell-protected slopes need less repair over their life than bare slopes.

Product Specifications at a Glance

The table below lists the main geosynthetics used on a corridor like the Delhi-Mumbai Expressway, with representative property ranges and the standards they are tested or specified to.

The grade for any location depends on wall height, soil, loading and design life, so the product has to be selected against the site design, not picked from a range.

For how a wall of this kind is put together, our guide to retaining wall design with geogrid and geotextile covers the job of each geosynthetic, sizing the reinforced block and the facing options.

Why Ocean Non Wovens for Expressway Projects

Ocean Non Wovens is an Indian manufacturer and supplier of geogrids, woven and non-woven geotextiles, geocells, HDPE liners and geobags, with materials tested to Indian and international specifications. For expressway packages that means one source for most of the geosynthetics in the table above.

Ocean Non Wovens supplies material for reinforced soil walls and steep slopes, subgrade and base stabilisation, slope protection and erosion control, drainage and water crossings, as well as defence infrastructure, airports, railways, water resources and industrial projects. If your project involves a geogrid retaining wall, geocell erosion control, separation, drainage or a water crossing, contact Ocean Non Wovens for help specifying the right grade for your ground conditions and structure.