Case Study on the Use of Ocean Uniaxial Geogrid 40 kN in Road Construction

Project overview

• Project Name: Road Project
• Location: Guwahati, Assam
• Product Supplied and Used: Ocean Uniaxial Geogrid 40 kN
• Quantity: 5,000 SQM
• Client Sector: Public road infrastructure (urban and peri-urban connectivity)

Ocean Non Wovens supplied 5,000 SQM of Ocean Uniaxial Geogrid 40 kN to strengthen a road section in Guwahati exposed to heavy vehicle traffic, seasonal flooding and variable subgrade. Guwahati is the main gateway to Northeast India and a logistics hub for Assam and its neighbours, and fast urban growth keeps adding traffic to roads built on difficult ground.

How a geogrid reinforces a road

A uniaxial geogrid is a polymer grid with its tensile strength concentrated in one principal direction; the 40 kN rating refers to its ultimate tensile strength per metre width in that direction. In road and embankment work, a geogrid:

• Increases the load-bearing capacity of weak subgrades
• Reduces lateral spreading of base and sub-base aggregates
• Spreads traffic loads over a wider area of subgrade
• Limits rutting and differential settlement

The mechanism is interlock. Aggregate particles seat into the grid apertures, so when a wheel load pushes the base outward, the grid ribs hold the stones in place. The base stays dense and stiff, and less load reaches the subgrade as concentrated stress. Giroud and Han (2004) set out a design method for geogrid-reinforced unpaved roads and working platforms built on this behaviour, and Indian guidance on geosynthetics in pavements is given in IRC SP:59.

The same family of geosynthetics is used for soil stabilisation, slope erosion control, drainage (geotextiles and geocomposites that pass water but hold soil) and lining of landfills and water containment.

Site conditions in Guwahati

Variable subgrade

Guwahati sits on the Brahmaputra floodplain, where alluvial soils vary in bearing capacity over short distances. Typical problems are:

• Low California Bearing Ratio (CBR) values
• High moisture sensitivity
• Seasonal loss of strength as groundwater rises and falls

Under repeated traffic, unreinforced pavements on these soils develop early rutting and cracking.

Monsoon and drainage

Assam’s heavy monsoon saturates subgrade layers, lowers soil shear strength and raises the risk of pumping, where traffic forces wet fines up into the base. Poor drainage and prolonged moisture are among the main causes of early pavement failure in high-rainfall areas, which is why IRC SP:42 (road drainage) and MoRTH Specifications give drainage so much attention.

Working in a busy corridor

• Short construction windows because of traffic management
• Irregular existing formation levels
• Difficulty compacting uniformly across changing soil strata

Reinforcement here has to tolerate minor subgrade inconsistencies and still improve performance.

Application of Ocean Uniaxial Geogrid 40 kN

Design intent and placement

The geogrid was installed at the interface between the prepared subgrade and the granular base layer. The design aimed to:

• Improve load distribution
• Reduce the required base thickness where feasible
• Increase resistance to lateral deformation under repeated axle loads

The 40 kN strength class was chosen for the expected traffic loads and the need for long-term performance in a high-stress corridor.

Installation and quality control

A geogrid performs only as well as it is installed. On site the work covered:

• Subgrade preparation: a reasonably level surface, free of sharp protrusions that would create local stress points on the grid
• Tensioning and alignment: laying the uniaxial grid with its strong direction oriented as designed relative to traffic, so its tensile strength is mobilised
• Overlap and anchorage: keeping specified overlaps and edge anchorage so the grid does not move during aggregate placement
• Aggregate placement: end-tipping and spreading the first lift of base material forward over the grid so it is not displaced or damaged

Quality checks covered visual inspection and alignment, and no construction traffic ran directly on exposed geogrid before cover was placed. Tracked or wheeled plant on bare grid can tear ribs or shift it out of position, which is where field performance most often falls short of design.

Long-term performance

Road geogrids must withstand repeated heavy-vehicle loading, temperature variation and long exposure to moisture and soil chemistry. Polymer geogrids are tested for creep, chemical resistance and durability, and long-term design strength is obtained by applying reduction factors (creep, installation damage, durability) to the short-term tensile strength, as set out by Koerner (2012) and FHWA NHI-07-092.

Reinforced pavement sections generally show:

• Lower rut depth over time
• Slower growth of surface cracking
• Less frequent structural rehabilitation

The geogrid adds material cost at construction, but longer service life and fewer interventions can lower whole-life cost. In high-rainfall regions like Assam, where water-related distress drives much premature pavement failure, that benefit is larger.

What the geogrid was designed to deliver

• Better subgrade support in weak soil zones
• Higher structural capacity of the pavement
• More resistance to monsoon-induced weakening
• More predictable performance under heavy traffic

References

• Giroud, J. P., & Han, J. (2004). Design method for geogrid-reinforced unpaved roads. Journal of Geotechnical and Geoenvironmental Engineering, ASCE.
• Koerner, R. M. (2012). Designing with Geosynthetics (6th Edition).
• FHWA NHI-07-092. Geosynthetic Design and Construction Guidelines. Federal Highway Administration, USA.
• IRC SP:59, Guidelines for Use of Geosynthetics in Road Pavements and Associated Works. Indian Roads Congress.
• IRC SP: 42, Guidelines on Road Drainage, and MoRTH Specifications for Road and Bridge Works, Government of India.
• ISO 10318. Geosynthetics terminology and definitions.

About Ocean Non Wovens

Ocean Non Wovens supplies geosynthetics for projects across India, from road reinforcement and soil stabilization to drainage and environmental protection. For base stabilisation under pavements, see also Ocean’s biaxial geogrid, or browse more case studies.