If the classic biaxial geogrid does not deliver the expected performance in your road project on soft soil — that is, if plate load tests or field tests show residual settlement greater than admissible under dispersed vehicular loads — the triaxial geogrid is the highest-performing option in the family for horizontal reinforcement. This MOLTEXO PP triaxial geogrid delivers 10 kN/m with an extended geometric structure in three directions (0°, 60°, 120°) and rigid triangular apertures, in a 3.95 m × 50 m roll. The difference from biaxial lies in how it confines the aggregate: triangular apertures work more efficiently on crushed stone and gravel under multidirectional loads than traditional square apertures.
The installation procedure is similar to that of biaxial — spreading, overlapping, temporary fixing, and layering fill — but with two relevant operational differences: the roll is narrower (3.95 m vs 6 m for biaxial), so the spreading plan changes, and aggregate confinement is activated with less initial compaction thanks to the triaxial geometry. This guide explains the operational differences compared to biaxial and when it is justified to use triaxial instead of standard biaxial.
Product specifications
The polypropylene triaxial geogrid is offered in a single standard presentation of 3.95 m wide by 50 m long, with an auditable strength of 10 kN/m per structural direction. The following table shows the full technical specifications of the only variant available:
| Specification | Value |
|---|---|
| SKU | 234123 |
| Material | Structural Polypropylene (PP) |
| Orientation type | Triaxial (extended geometry in three directions) |
| Tensile strength | 10 kN/m (0.7 kip/ft) per structural direction |
| Aperture shape | Rigid triangular (0°, 60°, 120°) |
| Roll width | 3.95 m (13 ft) |
| Roll length | 50 m (164 ft) |
| Area per roll | 197.5 m² (2126 ft²) |
| Chemical resistance | Inert to acids, alkalis, and soil microorganisms |
| Estimated service life | Decades in buried conditions |
| Main application | Subgrade reinforcement with multidirectional loads |
| Color | Black (with anti-UV carbon black additive) |
The sister guides for PP biaxial geogrid and PP uniaxial geogrid cover the other two orientations in the family: biaxial is the standard, lower-cost alternative for horizontal reinforcement on subgrades in reasonable condition, and uniaxial is specifically designed for MSE walls and slopes (directional loads with low creep).
Step-by-step for use
The following procedure covers the complete on-site installation cycle of the triaxial geogrid. The supervision of a qualified geotechnical engineer or site resident is always recommended; the following indications are for guidance and do not replace the specific engineering design for each project.
Validation of triaxial choice
Triaxial justifies its higher cost compared to standard biaxial in specific scenarios: very soft subgrades (CBR less than 2), complex vehicular traffic with loads in multiple directions (parking lots, heavy equipment maneuvering platforms, road crossings), or pavements where fill thickness is limited by elevation restrictions. If your project does not fall into one of these cases, biaxial fulfills the requirement at a lower cost. Before starting installation, validate with the resident engineer that the triaxial choice corresponds to the actual conditions of your site.
Subgrade preparation
Clear the surface of roots, large stones, and vegetation. Level the subgrade (no potholes larger than 5 cm) and compact to the minimum density specified in the project. Triaxial is somewhat more tolerant of minor subgrade irregularities than biaxial due to its geometry, but this does not exempt it from the requirement of proper foundation preparation. Avoid spreading on water-saturated soil: if the subgrade shows surface water after rain, drain it or wait for it to partially dry.
Roll spreading and overlap planning
The 3.95 m wide roll conditions the planning: for an 8 m wide platform, two rolls do not cover with clearance as with the 6 m biaxial. Plan the extension carefully so that longitudinal joints are not aligned with the ruts of expected traffic. Deploy taut, without folds or wrinkles: triangular apertures lose effectiveness when the geogrid is locally bowed.
Overlapping at joints considering triaxial geometry
Minimum overlap of 30 cm for longitudinal joints and 50 cm for transverse joints, same as with biaxial. The operational difference is that with triaxial geometry, the overlap offers a more gradual load transfer, so on very soft subgrades (CBR less than 1), the transverse overlap can be maintained at 75 cm instead of the 100 cm that biaxial would require. The practical rule of "if the subgrade sinks when stepped on, the overlap should be greater" still applies.
Triaxial benefits from combined use with non-woven geotextile on subgrades with fine particles present. The combination of geotextile underneath and triaxial on top creates a three-layer system (separation plus filtration plus reinforcement) that performs much better on problematic subgrades than any single element. The added cost of the geotextile is justified by the additional saving in granular aggregate thickness that this combination allows. For marshy subgrades or those with a CBR less than 1, this combined system is the recommended practice.
Filling and compaction with optimization curves
Dump the aggregate without driving machinery over the exposed geogrid: maintain at least 15 cm of aggregate between tracks or wheels and the geogrid. Compact in layers of maximum 30 cm. A particularity of triaxial is that aggregate confinement is activated with fewer compaction passes than with biaxial: if your standard procedure requires 6 compactor passes, with triaxial you can start evaluating density on pass 4 and adjust additional passes based on the results. This optimization saves compaction time on extensive projects.
Do not assume that triaxial is always better than biaxial. Triaxial is more expensive and provides a real advantage in specific scenarios (very soft subgrades, multidirectional traffic, thickness restrictions). In road projects with a subgrade in good condition and conventional vehicular traffic, biaxial 40 kN/m is more than adequate, and triaxial is over-specification. Geogrid selection should be based on the geotechnical report and load analysis, not on the idea that more expensive is better.
Is triaxial or biaxial the right choice for your project?
The choice between biaxial 40 kN/m and triaxial 10 kN/m depends less on the declared tensile value and more on the aperture geometry and the type of expected load. Ask the virtual assistant for: your subgrade's bearing capacity (CBR), expected traffic type (light vehicle, heavy, mixed), available fill thickness, and project budget. We will guide you to the correct choice without paying more for capacity that the project does not need.
Complementary Products
To complement the triaxial geogrid in subgrade reinforcement works with complex vehicular traffic or soft soils, the following products cover the most common adjacent needs:
The PP biaxial geogrid is the standard alternative in the family: same structural function (horizontal subgrade reinforcement) at a lower cost, indicated when the subgrade is in reasonable condition and traffic is not extreme. The non-woven PP geotextile complements the triaxial geogrid in subgrades with fine particles: the combination of geotextile below and triaxial above offers a separation, filtration, and reinforcement system that performs better than each isolated element. Metal rods are used for temporary anchoring of the geogrid during spreading and to ensure no displacement when machinery passes with backfill. The uniaxial PP geogrid is a solution for a different problem (MSE walls, slopes) and does not replace the triaxial geogrid in subgrade reinforcement.
Maintenance and Care
The triaxial geogrid buried under an aggregate and pavement layer requires no maintenance during its decades-long service life. The relevant care is for storage prior to installation: rolls should be stored horizontally, on a clean surface, and covered to protect from direct sunlight. Although PP contains an anti-UV additive, prolonged exposure to sunlight degrades the surface properties and could compromise interlocking with the aggregate.
During on-site handling, a particularity of the triaxial geogrid is that the roll format (3.95 m wide) makes it more susceptible to accidental transversal folds—a roll supported on a stone during storage can create a permanent crease that affects subsequent spreading. Always store rolls on flat pallets or a smooth surface. Visually inspect each roll before taking it to the site to identify creases, cuts, or edge damage that may have occurred during transport and unloading.
Frequently Asked Questions (FAQ)
When is the extra cost of triaxial vs biaxial justified?
The triaxial geogrid fulfills its differential function in three specific scenarios: very soft subgrades (CBR less than 2) where standard biaxial geogrid does not provide sufficient performance; complex vehicular traffic with loads in multiple directions (intersections, maneuvering platforms, commercial parking lots with cross-flows); projects where the fill thickness is limited by elevation restrictions or excavation costs. In conventional road projects on subgrades in good condition, biaxial geogrid is sufficient and more economical.
How do I calculate how many rolls I need if the roll width is 3.95 m?
Calculate the effective covered width by subtracting the lateral overlap (0.30 m per joint). For an 8 m wide platform with two parallel rolls, the effective covered width is 3.95 m plus 3.65 m (3.95 minus 0.30 overlap) equals 7.60 m, leaving 0.40 m uncovered; you will need a third partial roll. For large areas, the layout planning of the spreading has a significant impact on consumption: a small optimization of the roll arrangement can save one or two entire rolls. It is worth making a preliminary layout plan before ordering the material.
Can triaxial geogrid be used in MSE walls instead of uniaxial?
No. Triaxial geogrid is optimized for omnidirectional aggregate confinement on a horizontal plane, not for sustained directional resistance required by MSE walls. The declared strength of the triaxial geogrid (10 kN/m per direction) is much lower than that of the uniaxial geogrid (80 kN/m in the strong axis), and its creep behavior under sustained load is not calibrated for structural walls. Use uniaxial geogrid where the project requires MSE walls, reinforced slopes, or abutments.