Summer 2016

For the construction and repair of highways and railways in areas with poor soil conditions there is a series of tried and tested geosynthetic materials available: TenCate Mirafi® RSi Series. These materials provide the designer and contractor with an efficient and sustainable solution for both cost and time.
Two recent applications involve the repair of the state highway SR 53 in Wyandot County (Ohio, US) and the rail track at Rosetown in Saskatchewan (Canada). 

tencate mirafi rs580i
TenCate Mirafi® RSi Series (picture) are double-layer geotextiles used for base course reinforcement and subgrade stabilisation, for strengthening embankments, flood prevention and protection against erosion. Road builders can now use a single material for stabilising and strengthening the foundation of any type of subsoil in all circumstances. This reduces costs for the end-user and conserves natural resources optimally. It also reduces the time involved in repairing and constructing these transport connections. This certainly proved to be the case in the repair of state route SR 53 in Wyandot County (Ohio, US) and the rail track at Rosetown in Saskatchewan (Canada).

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Along the section of SR53 in Wyandot County, Ohio

The Ohio Department of Transportation (ODoT) is responsible for developing and maintaining all state and federal roadways in the state of Ohio. This project involved raising the grade and replacing the pavement along a section of SR53 in Wyandot County, Ohio. This section is underlain by a peat deposit, overlying a soft to medium stiff clay. Over the years the pavement had experienced freeze-thaw damage and uneven settlement, laterally and longitudinally, resulting in undulation requiring continual and expensive maintenance geosynthetics ohio 3

The initial desire was to remove most, if not all of the peat. This removal would have incurred very high costs. A second option involved the use of expanded polystyrene geofoam. This would have required extreme peat removal for load reduction, and there were concerns regarding the effect of the high groundwater level. ODOT then asked TenCate Geosynthetics America for assistance in developing a geosynthetic-reinforced system as a workable option.

geosynthetics ohio stenen over mirafi
The eventual solution consisted of two layers of TenCate Mirafi® RS580i within a 610 mm thick crushed limestone aggregate section for reinforcement and stabilisation. The design asphalt pavement section was then installed upon this Geosynthetic Reinforced Section (GRS). The cost savings from avoiding removal and replacing the peat, including dewatering, is estimated to be over $250,000. In addition, the project schedule was expedited by several weeks, reducing the amount of time needed for road closures and traffic detours. 

geosynthetics ohio situation after

More importantly, a safe road has been constructed that will last for many years.

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The CN Rosetown Subdivision is a section of Canadian National Railway Company (CN) track running between Roskin Junction (Saskatoon) and Kindersley (Saskatchewan). The track had to be lifted and realigned over twenty times between 2009 and 2013 due to ongoing track settlement, caused by extremely soft subgrade conditions and inadequate sub-surface drainage. A permanent speed restriction was imposed on trains operating through this area to ensure there were no derailments.

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However, despite all these measures there was still no improvement. For a permanent and cost-efficient solution it was decided to reinforce the area with geosynthetics.

In the 1920s, Arthur Newell Talbot (professor of municipal and sanitary engineering at the University of Illinois) developed a method that enabled designers to calculate the correct thickness of the rail track bed: the Talbot Equation. Here this should have been 120 centimetres, which proved not to be feasible in practice. The CN engineers approached TenCate Geosynthetics to help them construct a rail track bed reinforced with geosynthetics.

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The design engineers from TenCate advised the use of TenCate Mirafi® RS580i and by doing so were able to save a considerable amount on construction costs.  After removing the rail pads, sleepers and ballast, the soft clay subgrade was covered with a layer of TenCate Mirafi® RS580i. On top of this came a 400-600 mm layer of pit run material, covered by a second layer of TenCate Mirafi® RS580i for reinforcement, followed by a layer of sub-ballast. Atop the sub-ballast, ballast was added. 

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Finally, the rails and sleepers were put back in place. The entire project was completed without having to over-excavate the entire work area or change the grade of the track and with a minimum of additional materials.

Needless to say, the speed restriction has since been lifted by CN.

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Blue fabric (Tecawork Blue 65287)