Learn more about the ways pavement reinforcement and stabilisation can deliver multiple benefits
A geosynthetic reinforcement placed within an unbound granular layer can reduce the layer thickness required by one third and reduce rutting and differential settlement. Two mechanisms work to increase the elastic modulus and bearing capacity, resulting in improved resistance to deformation and rutting: the first is a confinement mechanism, which minimizes soil particle movement, the second is a tensioned membrane effect.
A road base is essentially a system for distributing wheel loads onto the subgrade soil. If the load is not properly distributed and spread onto a softer subgrade, the road may fail prematurely due to one or more of the following reasons:
- application of a single concentrated load exceeding the bearing capacity (undrained failure);
- accumulation of small permanent deformations (due to plastic strains), which in total cause excessive settlement, incompatible with the function (serviceability) of the road;
- deformations from shear failure of the structure.
The inclusion of properly selected reinforcement geosynthetics within the road base enables the reduction of the thickness of the construction layers “h” at constant values of: cohesion “c”; friction angle “φ” and the number of load cycles “N”.
Geosynthetics improve the performance of the base layer through:
- lateral confinement
- load distribution
- tensioned membrane effect
- separation effect.
The first three mechanisms are typically provided by geogrids (Macgrid WG and Macgrid EG), while the separation effect is provided by geotextiles. Therefore, geogrids stabilize the road base and increase its bearing capacity compared to an unreinforced situation, thus enabling savings on the thickness of the granular base. The benefits are numerous; cost effective, time efficient, reduced use of scarce resources, reduction in transportation of construction materials and therefore pollution, reduced carbon footprint and reduced maintenance.
To design the geogrid reinforcement of a road base, specific design methodologies have been developed. These are based on full scale tests, empirical formulas and diagrams, all available from existing literature. The design methodologies enable the designer to determine the required thickness of the unreinforced and reinforced road base, and to select the type and number of geogrid layers.
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