Tire derived aggregate as lightweight fill for embankments and retaining walls

Tire derived aggregate (TDA) is scrap tires that have been cut into 50 to 300-mm pieces. They have an in-place unit weight between 0.72 to 0.93 Mg/m(3). Due to their low unit weight, widespread availability, and relatively low cost, they are finding increasing use as lightweight fill for embankment construction on weak, compressible foundation soils. Moreover, they produce low earth pressure when used as backfill behind retaining walls. TDA has a shear strength that is comparable to or greater than the shear strength of typical embankment soils. Procedures to calculate the in-place unit weight and immediate compression of the TDA layer due to the weight of overlying soil are described. Two case histories are given. TDA was used to improve the stability of a 9.8-m high embankment constructed on weak marine clay. In addition, TDA was used as backfill to reduce lateral pressure on a cantilever retaining wall.