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Old forest roads in this region are closed to heavy axle loads when the frost begins to thaw from April-May every year. The roads are built with existing silty moraines and have low bearing capacity when the water content is high. Therefore it was necessary for the client to stabilise all access roads before trafficking commenced with 150 kN axle load vehicles.


Tensar TriAx was used to form a Mechanically Stabilised Layer constructed over existing access roads and several of the working platforms, with the objective of increasing bearing capacity.


Tensar TriAx was installed with a layer of 0-80mm crushed rock measuring 300mm thick placed and compacted on top of the geogrid. A surfacing layer of 0-32mm crushed rock measuring 50mm thick was also used. For some sections a second layer of TriAx geogrid was incorporated, depending on the sub-grade strength. Some of the existing roads suffered from very high water content, so geotextile under the geogrid was incorporated as an additional measure to prevent silt from contaminating the base material when compacted.

The TensarTech TW1 system was also chosen as a solution because of its structural flexibility.  Due to the dry laid construction of the facing, any anticipated post construction settlement could be accommodated without causing undesirable aesthetic facing issues.