Response and bedding factors of concrete pipe installed using the induced trench method utilizing tire-derived aggregate as a compressible fill layer

This study employs two-dimensional finite element analysis to investigate the influence of tire-derived aggregate (TDA) placement and backfill height on the structural performance of buried concrete pipes, with a focus on reducing maximum bending moments in the pipe wall. The analysis considers a 1.5 m diameter concrete pipe under varying backfill heights (2.0 to 10.0 m) and evaluates the effectiveness of TDA in inducing positive arching, as well as its impact on bedding factors. Key findings demonstrate that optimal TDA performance is achieved when positioned directly above the pipe crown, maximizing load redistribution through positive soil arching. The results indicate that increasing backfill height significantly enhances the beneficial effects of TDA in AASHTO Type 2 and Type 4 installations. For a 0.5 m thick TDA layer in Type 2 installations, the percentage reduction in maximum bending moment rises from 31% at 2.0 m backfill height to 42% at 10.0 m. Furthermore, greater TDA thickness substantially improves load attenuation—for instance, in Type 4 installations with an 8.0 m backfill height, bending moment reductions increase from 36% (0.5 m TDA thickness) to 60% (2.0 m TDA thickness). The results also showed that the TDA performed better in the Type 2 installation, as it achieved a higher percentage of bending moment reduction. Finally, new bedding factors have been proposed for different backfill heights and TDA layer thicknesses. These factors implicitly consider the positive soil arching and thus could be easily utilized by the pipeline designers.