NAUE Geosynthetics provided a single product reinforcement and separation solution for the upgrading of a 2km long unbound access road which runs across extremely soft subsoil conditions in south central British Columbia, Canada.

Building and maintaining unpaved access roads through the forests and grasslands of the Kamloops area of British Columbia can present contractors with considerable challenges for soil stabilization. Weak or variable soil conditions, combined with relatively high rainfall levels, mean that many roads and tracks suffer problems with rutting and inter mixing of the cover material into the subsoil.

When Argo Road Maintenance Inc., working for The British Columbia Ministry of Transportation, was recently contracted to upgrade a single lane gravel road in Monte Creek, they were faced with an existing road which had extensive deep rutting throughout.

Ongoing maintenance costs for the road were spiralling and, with road gravel mixing with the soil and disappearing with traffic, Argo knew that simply adding more aggregate would only provide a short term fix. A permanent solution was required that would provide both reinforcement and separation.

Argo Road Maintenance, along with the Ministry of Transportation, first considered using separate rolls of geo-fabric and bi-axial grids. However, because installation would have been complicated by using multiple rolls of 2 products with excessive overlaps, a single-roll, multifunctional product solution was sought. It was decided to appoint Naue Geosynthetics’ Canadian distributor, Brock White, to carry out trials using NAUE’s Combigrid® geogrids. Selected for the trials was Combigrid® 30/30 Q1 151 GRK3 – a single product geo-composite, developed specifically for ground stabilisation, which combines a 30kn polypropylene geogrid and a 150 gram per m2 geotextile.

Combigrid® is a composite product of a Secugrid® geogrid, with a needle-punched Secutex® non-woven geotextile firmly welded between the reinforcement bars. This technology has proven to be ideal for construction on soft soils, providing immediate reinforcement, separation, filtration and drainage, all in one product. Combigrid® geogrids have a high resistance to installation loads and can effectively prevent the migration of fine particles into the base course.

Combigrid® 30/30 Q1 151 GRK3 was approved for the project and a total of twenty 100m long rolls were supplied. Prior to installation of the Combigrid®, the full length of the existing road bed was graded to a level and, as the 4.75m wide rolls matched the road width, this meant that Argo Road Maintenance was able to rapidly lay the Combigrid® by simply rolling out the material without the need to employ specialist techniques or equipment. 150mm of aggregate cover was then spread and compacted to complete a mechanically stabilised access road, with significantly increased bearing capacity. Furthermore, because the road was a single lane construction with no place for trucks to turn around, the durability of Combigrid® was put to the test by having to withstand the constant toing and froing of heavy vehicles over its surface.

It was the first time that NAUE products had been employed by Argo Road Maintenance and the British Columbia Ministry of Transportation. Brock White reports that both parties were impressed with how Combigrid® performed in extremely soft soil conditions.

Project Name: Monte Creek Pinantan Gravelling
Location: Kamloops, British Columbia, Canada
Date: September 2014
Contractor: Argo Road Maintenance Inc.
Designer / Consultant: British Columbia Ministry of Transportation
Product: Combigrid® 30/30 Q1 151 GRK3