Numerical investigation of the bedding factor of concrete pipes under deep soil fill

The Indirect Design Method is often used to design buried concrete pipes. This method is based on linking the required strength of the buried concrete pipe to the laboratory strength of the pipe by using an empirical factor called the bedding factor. Hence, the bedding factor is key in the Indirect Design Method. However, a thorough review of the literature showed that the bedding factor has not received signification attention in previous studies. This study therefore reports the preliminary results of ongoing research investigating the bedding factors and the behaviour of concrete pipes under deep soil fill using validated numerical modelling. The results showed that the AASHTO bedding factors for type 2, type 3 and type 4 AASHTO installations are conservative, while the bedding factor is unsafe for pipes buried in type 1 installation with a backfill height of less than 2.4 m. Comparing the results of the present study with the British Standard bedding factors showed that these factors are overly conservative. Hence, both design standards should be updated to enhance the robustness of the design approaches and make the design of concrete pipes more economic.