Mechanical Stabilisation vs Reinforcement

Distinguishing between stabilisation and reinforcement is a key consideration for civil engineers when it comes to designing roads and platforms with geogrid.

As I discussed in our previous blog on tensile strength as a poor measure of stabilisng geogrid performance, the intended use of a geogrid, and how it interacts with the soil and fill layers around it, is far more important than its physical properties when it comes to designing roads and platforms and assessing their performance.

Some geogrids act in tension to provide a reinforcement effect, while ground stabilision geogrids, like  biaxial, triaxial and interax geogrids, confine and restrain particles to increase the performance of a granular layer in, or under a road, railway, working platform or other trafficked area.

The differences between stabilisation and reinforcement geogrids.

Certification bodies have recognised these differences, enabling manufacturers to obtain certification of geogrids for the function of stabilisation, even when the standards on which this certification is based may not yet consider the stabilisation effect. This benefits manufacturers, engineers, and ultimately client organisations; certification gives engineers the confidence that the products and systems they specify are fit for purpose and have been through rigorous, independent assessment.

The stabilisation function

The International Standards Organisation has recognised that the stabilisation function is distinct from the reinforcement function. Geogrid manufacturers can design products to optimise performance for either of these functions.

What is mechanical stabilisation?

ISO 10318 defines stabilisation as :

Improvement of the mechanical behaviour of an unbound granular material by including one or more geosynthetic layers, such that deformation under applied loads is reduced by minimising movements of the unbound granular material.

Put simply, a stabilisation geogrid interlocks with granular materials under load. The granular particles partially penetrate and project through the apertures and are confined. Particle rotation and movement is restrained by the geogrid. This forms a mechanically stabilised layer, which is stronger and stiffer than the unstabilised layer. The mechanically stabilised layer is capable of increased load spread, controlling differential settlement, reducing fill depths, capping weak deposits and increasing dynamic traffic loading and bearing capacity.

The improvement of the mechanical behaviour described in the ISO definition is not something that can be derived theoretically based on geogrid physical characteristics. Extensive full scale trafficking trials, as well as extensive project experience, have allowed Tensar to derive “stabilisation factors” for specific geogrid grade/aggregate type combinations, which, when applied to the granular layer, model the stabilising effect of the geogrid to allow engineers to benefit from reduced granular layer thickness and/or increase trafficking performance, as well as increased bearing capacity where heavy static loading is expected.

Available value includes both monetary and environmental savings to be quantified.

Visit our Knowledge Centre to find out more about the physical properties of geogrids.