Experimental study on earth pressure reduction of waste tyre bales used as a backfill for rigid retaining structures

Waste tyre-derived products, including whole tyres, tyre bales, shreds, chips and crumb rubber, have been widely used in geotechnical applications. In particular, tyre bales have considerable potential for use in the construction of a lightweight embankment or road foundation over soft ground, slope stabilisation or landslide repairs and the backfilling for retaining structures. Proper design of tyre bale structures requires a reliable strength analysis to ensure an adequate factor of safety. The analysis should utilise the properties of the tyre bales and the baled structures, which must be properly determined. A laboratory test programme was developed to determine the key strength parameters of a backfill made of tyre bales supplemented with a lightweight aggregate. Full-scale direct shear tests were conducted to define the interface shear strength between the tyre bales and the filling material. Earth pressure reduction analysis based on the experimental results was performed as well to assess the effectiveness of waste tyre bales used as a backfill for rigid retaining structures.