Biaxial vs triaxial geogrid, chosen by load and lifecycle.

Two families, different load-spreading mechanics.

The biaxial and triaxial geogrid families share polymer (polypropylene typically, integrally formed by punch-and-draw or extrusion) but differ at the aperture and rib geometry.

• Biaxial geogrid. Rectangular or square apertures, ribs running in two orthogonal directions (machine direction and cross direction). Tensile capacity is concentrated on the two principal axes; the diagonal direction is significantly weaker (typically 30-50 percent of axial tensile). Cell visually resembles a window-frame grid. Aperture typically 25-65 mm square for road-base applications.
• Triaxial / multi-axial geogrid. Hexagonal apertures formed by ribs in three orientations at 60 degrees to each other. Tensile and stiffness are radially distributed in all in-plane directions, rather than only on two axes. Cell visually resembles a chicken-wire or honeycomb. Aperture typically 40-65 mm across flats.

The headline performance consequence: under aggregate placed above the geogrid, lateral spread under load is resisted in all directions for triaxial, but predominantly on the two axes for biaxial. For omnidirectional or random-direction loading (port apron, mining haul road, urban yard), the triaxial radial behaviour is genuinely better. For predictable single-direction loading (plantation road in one alignment, container handling lanes), biaxial captures most of the reinforcement benefit at lower unit cost.

The trafficking trial data summarised.

Across multiple independent trafficking trials and full-scale instrumented sections (US Army Corps, UK Highways Agency, university research, plus accelerated pavement tester programmes), the consistent result for paved sub-base over weak subgrade under heavy axle loading is:

• Triaxial outperforms biaxial of comparable mass by 15-30 percent on aggregate-thickness saving at the same rut criterion, or equivalently 1.5-3x trafficking life at the same aggregate thickness.
• The margin grows with subgrade weakness: on CBR 5+ subgrade the two products are almost interchangeable; on CBR less than 2 the triaxial advantage is at the top of the 15-30 percent range.
• The margin grows with omnidirectional loading: single-direction trafficking narrows the gap; random-direction trafficking widens it.
• The margin grows with rut criterion: tight rut criteria (less than 25 mm for paved roads) favour triaxial; loose rut criteria (75-100 mm for unpaved roads) narrow the gap.

For Malaysian project work the practical implication is: triaxial for paved sub-base on weak subgrade, biaxial for unpaved working platforms and plantation roads on moderate subgrade.

Giroud-Han for biaxial, T-value for triaxial.

Biaxial geogrid: Giroud-Han 2004

The Giroud-Han 2004 method is the modern analytical reference for biaxial geogrid in unpaved and thin-paved road design. The method takes traffic (axle load, allowed rut depth, number of axle passes), subgrade CBR, and aggregate properties, and returns the required aggregate thickness with and without the biaxial reinforcement. The biaxial-product calibration factor is explicit. The method has been validated across hundreds of full-scale trials and is the JKR-acceptable approach for biaxial-product design submissions on Malaysian road projects.

Triaxial / multi-axial geogrid: T-value or radial-stiffness method

The original Giroud-Han model treats reinforcement as a layer with two principal axes; it does not represent the radial in-plane stiffness that gives triaxial its performance edge. Applying Giroud-Han to triaxial gives conservative (and economically unattractive) outputs. The industry has moved to a T-value method (or radial-stiffness-based approach) that uses an aperture-stability calibration factor measured at 2 percent radial strain. The method requires the radial-stiffness specification from the manufacturer datasheet plus a project-specific traffic-and-subgrade input. Outputs are validated against the same trafficking trial dataset that calibrates Giroud-Han for biaxial.

Paved highway: empirical uplift factors

For paved highway sub-base, both biaxial and triaxial reinforcement are normally credited through empirical pavement-design uplift factors on the design ESAL count or the equivalent design CBR. JKR-SPJ Section 7 and AASHTO PP46 alignment guides provide the framework. The uplift factor differs by product family and grade; the manufacturer datasheet maps to the design method.

Where each one fits best.

Three pitfalls we routinely flag.

Indicative unit costs across the families.

Indicative supply-only costs (delivered to site, Klang Valley reference, mid-2026), small project quantities. Project-specific quotes will differ.

The cost question is rarely answered by unit price alone; it is the per-m² aggregate-saving compared against unit cost. We run that calculation against project inputs as part of standard quoting.

Geogrid-related resources.