Geocell for subgrade
- Material: High-density polyethylene (HDPE) strip, welded ultrasonically to form a three-dimensional honeycomb structure.
- Core principle: Confines infill materials such as sand and gravel, restricts lateral spreading of fill under load.
- Performance: Improves subgrade bearing capacity, reduces differential settlement, disperses vehicle loads effectively.
- Construction: Lightweight, easy to unfold and fix on-site; adaptable to soft ground, sloped sections and uneven foundation.
- Typical applications: Highway & railway subgrade, parking lots, container yards, rural roads and temporary access roads.
Geocell for Subgrade
1 What a Geocell Is
A geocell is a three-dimensional honeycomb of polymer strips welded or jointed into open cells, delivered folded flat and expanded on site, then filled with granular or cemented material. In a subgrade it is a confinement layer: the cell walls stop the infill spreading sideways under load, so a loose aggregate becomes a stiff, load-spreading mattress — used to raise bearing capacity on soft ground, cut differential settlement at bridge approaches, thin out granular base and hold fill on slopes.
2 Why Geocell is Necessary for Subgrade
On weak, low-bearing-capacity subsoil, conventional granular base is prone to lateral outward flow of aggregate, excessive deformation, differential settlement and rutting under repeated vehicle loads. Simply thickening the gravel layer only raises project cost and often fails to meet long-term stability requirements.
The geocell cellular confinement system provides active lateral restraint to infill aggregates. It turns loose gravel/sand into a rigid composite slab, disperses wheel loads over a wider area, reduces vertical stress transmitted to the underlying soft soil, and controls permanent deformation.
It is necessary for the following scenarios:
1. Subgrade with soft clay, silt, peat or fill foundation with low CBR value. Without geocell, the granular layer will spread laterally and sink quickly under cyclic loading.
2.Temporary haul roads, construction access roads and heavy-load working platforms. These roads bear frequent heavy truck loads and require anti-rutting performance.
3. Areas with limited aggregate supply or high stone cost. Geocell can reduce the thickness of granular fill, saving raw materials.
4.Sections with strict settlement control requirements, such as road junctions, parking lots and light rail subgrade.
5.Sites where rapid construction is required; geocell shortens construction period compared with deep replacement or pile foundation schemes.
3 Advantages
▪ Lateral confinement: the wall carries the lateral thrust plain aggregate cannot, giving the layer an apparent cohesion and a modulus several times that of the same material unconfined;
▪ Load spreading: the mattress spreads wheel load wider, so vertical stress on the soft subgrade drops and the granular layer can be thinner;
▪ Compact to ship: a folded panel is a fraction of its deployed volume — a truck carries thousands of m² and no heavy plant is needed to place it;
▪ Works on poor ground: on peat, collapsible loess, permafrost or wind-blown sand it often replaces excavation-and-replace, and local fill can be used instead of imported graded stone;
▪ Drainage and friction: perforated strip drains pore water, textured strip grips the fill — both matter on wet, fine-grained subgrades;
▪ Durability: HDPE with 2.0–3.0 % carbon black resists acid, alkali, freeze-thaw and traffic fatigue for decades.
4 Product Range — GB/T 19274-2024
Table 1 Strip properties, by material and strip process
Property | Unit | PE extruded | PE stretched | PP extruded | PP stretched | PET extruded | PET stretched |
Tensile strength | kN/m | ≥ 20 | ≥ 100 | ≥ 23 | ≥ 100 | ≥ 30 | ≥ 120 |
Tensile yield strain | % | ≤ 15 | — | ≤ 15 | — | ≤ 15 | — |
Tensile strain at break | % | — | 8–20 | — | 6–15 | — | 8–20 |
Carbon black content | % | 2.0–3.0 | 2.0–3.0 | 2.0–3.0 | 2.0–3.0 | 2.0–3.0 | 2.0–3.0 |
OIT at 200 °C | min | ≥ 20 | ≥ 20 | ≥ 20 | ≥ 20 | — | — |
Tensile load stress crack | h | ≥ 300 | — | — | — | — | — |
Weathering retention, 500 h | % | ≥ 80 | ≥ 80 | ≥ 80 | ≥ 80 | ≥ 80 | ≥ 80 |
Chemical resistance retention | % | — | — | — | — | ≥ 80 | ≥ 80 |
Table 2 Cell dimensions and junction strength
Cell height H | Tolerance | Strip thickness E / S | Junction grade | Pull-out | Shear | Peel |
H ≤ 100 mm | ± 2 mm | ≥ 1.0 / ≥ 0.45 mm | I / II | ≥ 20 / 36 | ≥ 20 / 36 | ≥ 14 / 18 |
100 < H ≤ 200 mm | ± 3 mm | ≥ 1.0 / ≥ 0.45 mm | III / IV | ≥ 100 / 160 | ≥ 80 / 100 | ≥ 40 / 80 |
200 < H ≤ 250 mm | ± 3 mm | ≥ 1.0 / ≥ 0.45 mm | V | ≥ 240 | ≥ 120 | ≥ 120 |
5 Selection by Condition — Which Height, Grid and Joint
Table 3 Condition → height, grid, grade and the reason
Condition | Height | Grid / strip | Joint grade | Why |
Light-duty subgrade, car parks, low embankment (CBR ≥ 3) | 100 mm | 400–500 mm | I–II | Thin granular layer over competent ground; a shallow cell stops lateral spreading and more height only costs fill. |
General highway and railway subgrade, soft ground 1 ≤ CBR < 3 | 150 mm | 330–400 mm | III | The workhorse: aspect ratio near 0.4 gives the stiffness gain, textured strip grips the fill, and 150 mm matches a 25–30 cm compacted lift. |
Heavy-haul road, container yard, bridge approach, deep soft clay (CBR < 1) | 200 mm | 330–400 mm | IV–V | Higher cells resist punching into very soft ground and bridge at an abutment; perforations let pore pressure dissipate during consolidation. |
Very thick fill or high differential settlement, pile-supported embankment | 200–250 mm | 330 mm grid, | V | Maximum confinement and junction strength — the layer acts as a stiff platform handing load to the piles, not the fill. |
Expansive or collapsible soil, permafrost, wind-blown sand | 150–200 mm | 330–400 mm | III–V | Very high strip strength at low thickness, so the layer carries tension across a shrinking or thawing zone without losing confinement. |
6 Installation Points
▪ Prepare the formation: compact to the design value (≥ 93 % is the common subgrade requirement), remove sharp stone, cut steps into slopes steeper than 1:5; no soft pocket under the panel.
▪ Expand and fix: expand each panel fully and peg it so cells stay square, not pulled into diamonds; join adjacent panels with the supplied couplers or U-pins, not just side by side.
▪ Fill and compact: fill in 20–30 cm loose lifts, compact each; fill stands 2–3 cm proud of the cell wall before rolling so the roller loads the fill, not the strip. Particle size within 10 cm of the geocell ≤ 8 cm — a larger stone bridges across cells. No plant on an unfilled or laid panel.
▪ Edge and interlayer connection: join layers with rivets or U-pins and, in walls, 0.6 m Ø 10 bars at 2 m × 1 m; extend toe and crest cells 0.5–1.0 m and bury.
▪ Inspection: sample strip strength every 5000 m²; check deployed grid size, junctions and fill compaction — a geocell that passes on material but fails on compaction has delivered nothing.
7 Geocell for Subgrade FAQ
1. Q: What is the reinforcement mechanism of geocell for subgrade?
A: It forms a rigid honeycomb confinement system. The cell walls lock gravel or sand infill, restrict lateral displacement of aggregates, increase the overall modulus of the fill layer and spread traffic loads to reduce settlement.
2. Q: What filling material is suitable for geocell?
A: Crushed stone, gravel, sand, recycled aggregate are commonly used. Sharp oversized rocks and sticky wet clay are not recommended.
3. Q: What height of geocell is usually used for subgrade reinforcement?
A: Common heights: 50 mm, 75 mm, 100 mm, 150 mm. Higher cells are selected for softer foundation or heavier load conditions.
4. Q: Can geocell be used on steep slopes besides subgrade?
A: Yes. It is widely applied for slope erosion control and retaining structure filling, but the design load and welding strength shall meet slope requirements.
