In this article, vertical and horizontal deflections in 18 thermoplastics pipes buried under high fills within the scope of Ohio University project were analyzed by using the Iowa equation which is a traditional approach in design of buried flexible pipes, approaches derived from this equation and the method developed by German Standards. During the investigation, the results obtained through these methods were evaluated by taking pipe and backfill material into account.  Furthermore, the behavior of thermoplastic pipes and burial medium were 2D modeled and analyzed with finite element method. The results determined through analyses conducted with the finite elements method as well as empirical approaches were compared with field measurements and evaluated.

Key words: Flexible pipe, deflection, modified Iowa equation, German method, ATV, PLAXIS analysis.