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Unpaved roads reinforced by geotextiles over soft subgrade soil have a greater resistance to traffic loads and allow constructions of a more efficient and sustainable nature than conventional methods. 

Road networks are being constantly expanded and so the number of unpaved roads on soft surfaces, featuring massive ruts and posing a high safety risk to road traffic, are on the rise. 

On unpaved road sections, the aggregate sub-layer lying on top of the soft subgrade can experience horizontal movement under traffic loading, leading to a reduction in aggregate thickness and compromising the overall stability. 

The new evidence regarding the interactions worth considering for this range of products, will allow woven geotextiles to be put to even better use in road construction than ever before.

Nisrine Abou Chaz, PhD Candidate, Research Manager Reinforcement at Solmax

Higher performance due to geotextiles 

As many years of experience have shown, installing geotextiles at the interface between the soft subgrade layer and the granular platform leads to significant improvements: The geotextiles can reduce the thickness of the required base course resulting in fewer settlement effects and less rutting. The infill material is optimally compacted, the road has a higher load-bearing capacity and its overall service life is increased. Installing these geosynthetics leads to an improvement in the performance of unpaved roads through separation, reinforcement and stabilization. 

Experimental and numerical studies for design optimization 

However, the heterogeneous subgrade and base course layers, the volatile properties of the road structure when exposed to cyclic traffic loads, and the various other parameters entailed in each road project affect the behavior of the platform, making it difficult to design a maximally effective solution with geotextile reinforcements. 

Experimental and numerical studies have now been conducted to investigate the underlying mechanisms in detail in order to optimize the structural design. A test carried out on an unpaved road, investigated the performance of the reinforcement when exposed to cyclic vertical loads and traffic loads. 

Geotextiles reduce settlement and base course thickness 

The results from the tests demonstrate effectively that the road section reinforced by geotextiles withstands recurrent loads better than roads constructed conventionally without geotextiles. The geotextile reduces both the settlement on the base course surface and the settlement on the subgrade surface. Furthermore the study demonstrates that a 30 cm thick granular platform reinforced with geotextiles with an optimized young’s modulus, performs better than a thicker unreinforced platform of 50 cm under vertical cyclic loading. Therefore, this study demonstrated again the bearing capacity improvement due to the use of geosynthetics and in particular made it possible to quantify the reduction of the base course thickness in accordance with the soil conditions.  

Applying the experimental and numerical results  facilitates the optimized use of geotextiles for stabilization in road construction.  

Environmentally friendly and sustainable  

This research work shows that using adapted and optimized geosynthetics facilitates the reduction of the quantity of granular fill and consequently the environmental impact of the CO2 emissions since fewer trucks are required for material transportation. 

It confirms, as shown in other studies, that geosynthetics inherently require fewer resources and produce fewer emissions in subgrade stabilization projects by approximately 40% when considering the total lifecycle from cradle-to-grave compared to non-stabilized solutions.  

At the end of the life cycle of an infrastructure project, the geotextile can be de-installed in a controlled manner and ultimately recycled, which promotes a circular approach.

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Nisrine Abou Chaz, PhD Candidate, Research Manager Reinforcement, Sales & Marketing EMEA