Recycled Tires as Lightweight Fill

The New Brunswick Department of Transportation (NBDOT) is incorporating shredded tires into the reconstruction of a highway embankment. These shredded tires (referred to as Tire Derived Aggregate or TDA) have a much lower unit weight than conventional earth fills and provide an economical solution to reducing the load of an embankment constructed over soft foundation soils. Prior to choosing the TDA redesign, NBDOT considered stabilization options including; replacing soft soils with granular fill, using stone columns, and reducing loads with geofoam as lightweight fill. The original 14 metre high and 140 metre long embankment section failed during construction in 2006. To significantly reduce the load and keep the original design height of the embankment, 1.6 million scrap tires will be recycled into TDA lightweight fill. TDA will be placed in two separated 3 metre thick layers within soil fill to form the lightweight embankment. The geotechnical, economic and environmental benefits of selecting the TDA design are discussed in this paper. Also, design precautions, TDA construction and materials handling for Stage 1 of the TDA embankment are presented. The final stage of the construction will be completed in the summer of 2008.