The response of buried pipes to UK standard traffic loading

The current design practice in the UK for estimating the soil pressure on a buried pipe under traffic loads is based on a simple equation derived using a Boussinesq solution. In order to test and verify this equation, and study the effect of pipe diameter and backfill height for rigid (concrete) and flexible (PVC) pipes, a study has been conducted using three-dimensional finite element modelling. It was found that increasing the diameter of the concrete pipe nonlinearly decreases the maximum vertical displacement, while the relationship between the concrete pipe diameter and the maximum thrust force was found to be dependent on the backfill height. Increasing the diameter of the PVC pipe linearly increases the displacement and the maximum thrust force. The effect of traffic live load on the maximum thrust force becomes insignificant for a cover depth larger than 2 m and 3 m for the concrete and PVC pipes, respectively. The results indicate that there are significant issues with the maximum soil pressure equation used in the British Standard. A new equation has been developed using numerical modelling results and using a regression analysis to predict the maximum soil pressure on a buried pipe based on backfill height.