Winter 2015

TenCate Mirafi® PET geotextiles for walls of ammunition depot Bedford

The Canadian Forces Ammunition Depot Bedford (Nova Scotia, Canada) houses the ammunition for the ships of the Maritime Forces Atlantic Formation of the Canadian Navy. Some years ago new geosynthetic reinforced blast walls were constructed using TenCate Mirafi® high strength PET geotextiles. 

The ammunition depot sits on a hillside that faces Halifax Harbour. Due to its location on the hillside, concrete blast walls are required in front of each ammunition bunker to absorb any blast that might occur  to shield the harbour and surrounding area from the force of the blast. Regulations have changed since these walls were originally constructed in the 1950s, and new regulations require the blast walls to be constructed of a material that would not fragment into pieces larger than 19 mm if hit by an explosive blast. 
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Mitchelmore Engineering was responsible for designing and selecting the materials for the three walls that were to be built. The criteria that had to be met were: maximum particle size of 19mm when exposed to blast, economics, a design life of 20 years, ease of construction and material availability. After careful evaluation, a geotextile-wrapped wall was chosen. This geotextile option allowed for the face and reinforcement to be of a single material. 

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If exposed to a blast, the maximum particle size would be limited by the gradation of the contained granular backfill which was (19 mm). It would be easy to construct using temporary forms, and by spraying the exposed geotextile face with an asphalt emulsion after completion, UV stability would not be an issue. In addition, the new blast walls would have to be freestanding, thus requiring four exposed sides. 

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TenCate Mirafi® PET 100 polyester geotextile met all the technical specifications and requirements of the design. In accordance with the contract documents, TenCate Geosynthetics provided a qualified technician, experienced in the construction of these types of wall systems, to provide on site technical support to the contractor. Each blast wall is 72 m x 9 m x 6 m high and was constructed of 11 lifts of TenCate Mirafi® PET100 geotextiles. The use of this material enabled the engineer to design a structure that was cost effective yet had the ability to absorb extreme explosive forces. 

Blue fabric (Tecawork Blue 65287)