NWR Doubling Project KTWS–NNL: Reinforcing Railway Infrastructure with Geocell Technology

Project overview

North Western Railway (NWR) is doubling the line between Kathuwas (KTWS) and Narnaul (NNL) in southern Haryana, a project known as the “NWR Doubling Project KTWS–NNL”, to add capacity and reduce congestion for freight and passenger traffic. For one part of this work, Ocean Non Wovens supplied and installed 380 SQM of Ocean Geocell 356×150 mm to reinforce the sub-base in critical zones of the embankment and track substructure.

Why geocell for KTWS–NNL

Doubling projects build a new embankment alongside a working line, often on subsoil with poor bearing capacity, mixed composition (clays, silts, sandy loam) and a tendency to settle or become waterlogged. The conventional fixes are thick granular sub-bases, deep soil replacement or stone columns, all of which cost time and imported material.

A geocell is a three-dimensional honeycomb of HDPE strips. Once expanded and filled, its walls confine the infill and stop it spreading sideways under load. That confinement raises the shear strength and bearing capacity of the layer, so it behaves as a stiff mattress that spreads the dynamic loads from passing trains over a wider area of subgrade and limits deformation under repeated loading. On the KTWS–NNL stretch, with variable soils, seasonal weather swings and rising traffic, that made geocell a good fit.

About Ocean Geocell 356×150 mm

Ocean Geocell 356×150 mm is an HDPE cellular confinement system for sub-base and subgrade reinforcement. In the usual geocell designation, 356 mm is the spacing between welds along each strip (which sets the size of the expanded cell) and 150 mm is the cell depth. Properly filled and compacted, it gives good load distribution and confinement. Choosing this size allowed the team to:

• Use locally available infill (sandy loam, granular soil), reducing imported aggregate and cost.
• Keep the reinforced layer slim, so embankment levels stayed within railway design norms. On a doubling project the new formation has to match the existing track levels.
• Get the confinement and load spreading needed without overspecifying the section.

Installation

1. Subgrade Preparation: the native soil was graded and compacted, and loose or soft pockets were found and densified to give uniform bearing.
2. Geocell Deployment: geocell sections were laid out, expanded on site and pinned in full contact with the subgrade.
3. Infill with Locally Available Material: local soils (silty loam, sandy loam or mixed fill) were used in place of imported granular aggregate. The confinement makes such marginal fills serviceable.
4. Compaction in Layers: the infill was compacted in layers with vibratory compactors to the required density. The cell walls keep the compacted infill from spreading under cyclic loading.
5. Final Capping and Integration with Track Structure: the reinforced sub-base was capped to the embankment design, giving a stable platform for ballast and track.

This reduced the need for high-grade aggregate, sped up construction and kept the embankment stable under heavy axle loads. In general practice, cells are slightly overfilled before compaction so the roller works on soil rather than on the cell walls, and plant does not run on unfilled cells.

Site observations

Subgrade variability and seasonal stress

The soil profile changed considerably along the KTWS–NNL stretch, from sandy loam to silty clay, with patches of loess-like, compressible subsoil. Summer heat dries and cracks the soil; monsoon rain softens it and causes settlement. The geocell kept the infill locked in place through both conditions, preventing lateral migration, collapse or uneven settling.

Marginal infill

Using local fill instead of high-grade aggregate saved material cost, cut the trucking (and the emissions that come with it) and shortened the programme. The cellular confinement turned that fill into a load-bearing composite layer.

Drainage

Where waterlogging risk was higher, from agricultural runoff or shallow groundwater, subgrade drainage was sorted out before the geocell went down. A geocell does not drain a formation by itself; combined with a well-compacted subgrade and proper capping, it keeps the sub-base stable when it does get wet.

Maintenance

Unreinforced granular sub-bases tend to suffer ballast contamination, lateral spreading and settlement under repeated train passes, which drives up track maintenance. A confined sub-base resists those deformations, so the lifecycle cost of the line, counting maintenance, stability and material, compares well with conventional construction.

Results on KTWS–NNL

The 380 SQM was a small quantity relative to the total track length, placed in critical sub-base zones:

• Bearing capacity: the reinforced sections carry heavy axle loads with lower risk of differential settlement or subgrade punching.
• Materials: local fill meant less imported material and transport.
• Speed: geocell reinforcement was quicker than deep granular fill or soil replacement, helping keep the doubling work on schedule.
• Stability: the confined sub-base is less prone to deformation, which supports longer maintenance intervals.

Ocean Non Wovens supplies geocell, geotextile, geomembrane and related geosynthetics for railways, highways, landfills, slopes and water containment. More project examples are on the case studies page.