Geocells

Geocells are expandable honeycomb panels of HDPE strips that are spread out on site, filled with soil, aggregate or concrete, and compacted. The cell walls confine the infill so it cannot spread sideways under load or wash away on a slope. Ocean Geosynthetics manufactures perforated, textured HDPE geocells (also called HDPE geo cells or cellular confinement systems) in five cell sizes and cell depths from 75 to 300 mm, for road bases, slopes, channels, retaining walls and load support.

What are geocells?

A geocell is a three-dimensional cellular confinement system. HDPE strips are ultrasonically or thermally welded together at regular intervals; when the panel is pulled open it forms a mattress of connected cells, each a few hundred millimetres across. The function is stabilisation and reinforcement: the cells turn loose fill into a stiff, interlocked layer.

Geocells differ from geogrids, which are flat and rely on particles locking into apertures. A geocell holds the whole depth of the infill inside its walls, which is why it works with poorer infill and on slopes where a flat grid would not hold the soil.

How geocells work

• Lateral confinement: when a load presses down on the infill, the infill pushes outward against the cell walls. The walls resist through hoop tension and the passive resistance of the neighbouring cells, so the infill keeps its compaction and its stiffness rises.
• Load spreading (mattress effect): the filled panel acts as a semi-rigid slab, spreading a wheel or foundation load over a wider area of subgrade. Vertical stress on the subgrade falls, which reduces rutting and settlement.
• Use of local or marginal infill: because confinement adds stiffness, locally available granular material can often replace imported aggregate, and the granular thickness can be reduced.
• Erosion resistance: on slopes and in channels, the cell walls stop infill moving downslope or being carried away by flowing water, and keep topsoil in place while vegetation establishes.
• Drainage: perforations in the walls let water move between cells, so a granular-filled layer stays free-draining.

What are geocells made of?

Most geocells, including Ocean’s, are made from high-density polyethylene (HDPE) with carbon black for UV stability. Other polymers, such as polyester or novel polymer alloys, are also used by some manufacturers. Ocean’s strips are textured to increase friction with the infill and perforated for drainage, with a nominal sheet thickness of at least 1.52 mm after texturing. The strips are welded at fixed spacing; the weld spacing sets the cell size.

Ocean HDPE geocell range

Ocean supplies five cell sizes, OG/GC-330 to OG/GC-712 (the number is the weld spacing in mm), each in seven depths. Smaller weld spacing gives smaller cells and more confinement; larger spacing covers more area per panel. Material properties and dimensions are below.

Weld (seam) strength of geocells is tested to ISO 13426-1, which covers the strength of internal junctions in geocells; ask for seam test data with your quote. IRC:SP:59-2019 covers the use of geocells in road pavements in India.

Applications

• Roads and unpaved access tracks: base and sub-base stabilisation over weak subgrades, including haul roads, rural roads, temporary site roads and hill roads, with less rutting and reduced aggregate thickness.
• Railways: stabilising the sub-ballast and formation to correct surface degradation of the track bed.
• Ports, container yards, parking areas and airports: load support for heavy, concentrated loads on soft ground.
• Slope protection: topsoil-filled geocells on cut and fill slopes, including highway slopes in hilly areas, hold soil in place and support vegetation.
• Channel and canal lining: concrete- or stone-filled geocells protect channels and riverbanks from scour by flowing water.
• Retaining walls: stacked, filled geocell layers form flexible gravity walls with a free-draining face that can be vegetated.
• Foundations and load transfer platforms: a geocell mattress under embankments and footings on soft soil spreads load and reduces settlement.
• Landfills and reservoirs: holding cover soil on landfill caps and protecting reservoir embankment slopes.

Sectors include roads and highways, railways, mining, ports and aviation, coastal works, landscaping and civil engineering generally.

How to choose cell size and depth

• Load support: heavier and more concentrated loads call for smaller cells and deeper sections, filled with well-graded granular material. The design should be done for the subgrade strength and traffic.
• Slopes: steeper slopes and higher rainfall need smaller cells and anchoring with stakes or tendons. Gentle slopes with topsoil and vegetation can use larger cells and shallower depths.
• Channels: depth and infill depend on flow velocity. Concrete infill is used where velocities are high; stone or vegetated soil where they are lower.
• Infill: the infill should be compactable and its maximum particle size small enough to fill the cells properly. Fines-rich soil gives less stiffness than granular fill.
• Subgrade: place a nonwoven geotextile under the geocell on fine, wet subgrades to separate infill from subgrade soil.

Installation basics

• Prepare and compact the subgrade to the design level and lay the separation geotextile if specified.
• Expand each panel to its full nominal size and hold it open with stakes or a stretcher frame. On slopes, anchor the panel at the crest and with stakes or J-pins across the face.
• Join adjacent panels with staples or ties so the cell walls line up and the system acts as one layer.
• Fill the cells, limiting drop height so walls are not damaged, and overfill slightly so the compacted surface sits at or just above the cell walls.
• Compact the infill. For roads, keep plant on filled cells, never on empty panels, and add any wearing course or pavement layers as designed.

History of geocells

Geocells were developed in the late 1970s by the US Army Corps of Engineers at the Waterways Experiment Station in Vicksburg, Mississippi, to let military vehicles cross sand quickly. Early prototypes used wax-coated kraft paper, plastic drainage pipe held with staples, and aluminium. The Corps then worked with Presto Products, a plastics manufacturer, which developed a method of welding polyethylene strips into a cellular grid; testing found HDPE gave the most consistent welds and strength. Commercial geocell systems reached the civil engineering market in the early 1980s, and since the 1980s they have been used widely outside the military for roads, slopes and channels.

Frequently asked questions

What is the difference between a geocell and a geogrid?

A geogrid is a flat grid that reinforces by interlock with aggregate. A geocell is a three-dimensional mattress that confines its infill over its full depth, so it works with poorer infill and on slopes and channels.

What cell depths does Ocean supply?

75, 100, 125, 150, 200, 250 and 300 mm, in each of the five cell sizes.

What can geocells be filled with?

Granular aggregate or local soil for load support, topsoil for vegetated slopes, and concrete or stone for channel linings and hard surfaces.

Why are the cell walls perforated and textured?

Texture increases friction between the wall and the infill. Perforations let water drain between cells and improve the bond between infill in adjacent cells.

How much area does one panel cover?

It depends on the cell size: from about 14.9 m² for OG/GC-330 up to about 35.1 m² for OG/GC-712, as listed in the dimensional table.

Related products: plastic cell filled concrete for low-cost concrete pavements, erosion control mats for slope surfaces, and geogrids. Send us the application, subgrade details and area for a cell size and depth recommendation.